Selective Regimes Shaping Morphologies

Last month, I wrote on the Dendrosenecios and their diversification throughout the tropical mountains of eastern and central Africa.  The Dendrosenecios were incredibly well adapted to their harsh environment.  The remarkable features that they show, such as: the large pith volume, the marcescent foliage and nyctinasty were adapted to their equatorial, tropical alpine environment.  Interestingly, a few other places around the world, such as Hawaii and the tropical Andes have similar climates.  In response, other plants within the family Asteraceae have developed the same adaptations as the Dendrosenecios of Africa.  This is known as convergent evolution, which can be simply defined as similar adaptations to similar environments by members of distantly related lineages.

Figure 1.  Asteraceae convergent evolution: The Silversword Alliance of Hawaii (left) and the Dendrosenecios of Africa (right).

This month, I will look at a local example of convergent evolution that is relevant to my Honours Research Project, focusing on scatter-hoarding in the Proteaceae.  There are three major guilds of seed dispersal in the fynbos, two of them are serotiny and myrmechocory.  Serotinous seeds are typically held in the plant canopy and dispersed by wind, post-fire.  Myrmechocorous seeds have a nutritious tissue called an elaiosome attached to the seed hull.  Ants drag these seeds underground and consume the elaiosome, leaving the seed intact and protected from seed predators and fires.  The third, scatter-hoarding, is a less understood dispersal guild in the fynbos.  Seeds of this guild are generally large with thick hulls, lacking a wing or elaiosome.

Figure 2.  A typical scatter hoarding seed.  This is an image of the tooth marks of Rhabdomys pumilio, known as the number one seed predator, on the hull of a Ceratocaryum argenteum (Restionaceae) seed.

Scatter-hoarding takes place when rodents are presented with a glut of seeds and do not have the appetite to eat them all.  In certain species, a behavioral response is then triggered – they bury the remaining seeds, typically away from where the seeds were found.  They will then rely on their smell and memory to relocate the seeds they have buried, extending their use of the food source.  Of course, not all of the seeds are relocated, allowing a dispersal advantage to the lucky seeds that got away, as they will now not need to compete with their mother plant. 

So, within the broader scope of scatter-hoarding, are a number of interesting questions that can be asked about this behavior.  A recent area of research has been the selection for specific seed traits, such as hull thickness, by predating and scatter-hoarding rodents.  Rusch et al (2012) expected that rodents would preferentially disperse and cache large, thick hulled seeds but consume small, thin hulled seeds as they are found. 

Initially, the natural variation of the two seed traits was quantified by extensive measurements of all parameters for Leucadendron sessile seeds – the suncone bush.  The research team then used an interesting technique to better understand seed selection based on hull thickness and seed size – because it is rather difficult to determine the thickness of the hull or fleshiness without breaking the hull open.  Firstly, the seed hulls of L. sessile seeds were removed and replaced with a non-toxic, plumber’s putty as a simulant of a woody hull.  This way, the thickness of the seed hull was controlled for.  The putty was placed on the naked seeds at 1, 2 or 2.5mm.  Next, macadamia nuts were used as a replacement for L. sessile seeds, because their size could be controlled for.  The macadamias were sanded down to either be at the recorded smallest, average or largest sizes and then covered in a standard 2mm hull thickness.  Seeds were then placed out overnight at seed stations at the research site.

Figure 3. Acomys subspinosus - the Cape spiny mouse. 

The biggest culprit of seed removal was suggested to be Acomys subspinosus or better known as the Cape Spiny Mouse.  The results of this study are shown in the two figures below.  Figure 4 shows the fate of seeds in the hull thickness experiment.  Figure 5 shows the fate of seeds in the seed size experiment.  Interpretation of the results can be seen in the figure captions.

Figure 4.  Fates of thin-hulled, average-hulled and thick-hulled L. sessile seeds after a 12 hour exposure to Cape Spiny mice in the field.  Thin-hulled seeds were eaten most often, average-hulled seeds cached and thick-hulled seeds were not dispersed. 

Figure 5.  The fates of small, average and large macadamia seeds after exposure to the Cape Spiny mice for 12 hours in the field.  Small seed were predominantly eaten, average sized seeds cached and large seeds not dispersed.

It is clear from this research that rodents have a preference for which seeds they chose to disperse or consume.  Average sized seeds with an average size and hull-thickness were preferentially dispersed.  While seeds that were small or thin-hulled were most often consumed at the seed stations.  Large or thick-hulled seeds were frequently left at the depot sites.  The authors of this research suggest that the energetic cost of handling, transport and burial are the reasons for their preferential choices.  The importance of these results is that it suggests that rodents exert stabilizing selection against the extremes of seed size and hull thickness for L. sessile seeds.

In the extreme environments of the tropical alpine zone, the climate creates a selection regime that leads to the distinct morphological features that are shown by members of the Asteraceae.  Around my home, Cape Town, fynbos plants such as those members of the Proteaceae and Restionaceae are exerted to a selective regime by seed consuming and dispersing rodents.  Seed predators are common throughout the fynbos and therefore it has been suggested that the scatter-hoarding guild of seed dispersal is more common than is currently understood.  Very few of the relationships between plants and their scatter-hoarding rodents have been documented, which allows for exciting future research for a young ecologist like me. 

(Rusch, U.D., Midgley, J.J., Anderson, B.  2013.  Rodent consumption and caching behaviour selects for specific seed traits. South African Journal of Botany.  84: 83-87)

Giant Senecio Diversification in East African Tropical Mountains

For June I will be going through an article that further follows my love for mountains and their amazing ecology and vegetation.  In Equatorial Africa, there is a group of particularly unusual plants that grow within an altitude band from 2500 to 4600m on 10 mountains in 5 countries, the giant senecios (known as the genus Dendrosenecio).  These 5 countries are the Democratic Republic of Congo, Rwanda, Uganda, Kenya and Tanzania and are all homes to mountains that are taller than 3300m and fall within 4˚ of the equator.

Figure 1. Mount Kilimanjaro in the foreground and Mount Meru in the background.

What makes these senecios remarkable is their extraordinary size, with some growing up to 6m in height.  What makes this truly amazing is that their closest, non-montane relatives rarely grow larger than a metre tall.  The Dendrosenecio’s size is not their only amazing characteristic.  They have a host of morphological features that allow them to successfully inhabit their extreme habitat.  So, besides their giant rosette growth form, they have a large pith volume, marcescent foliage and nyctinasty. 

Figure 2.  The relative size of the giant senecios.

To translate: the large pith volume allows them to store large amounts of water; marcescent foliage means that they retain withered or dead foliage for insulation; and nyctinasty is the response of leaves to cold, meaning they close once temperatures are too cold for photosynthetic activity.  Furthermore, members of Dendrosenecio secrete polysaccharide fluids which act as a natural anti-freeze.  These features have evolved independently in the montane giant lobelias (also African) and the Andean genus Espeletia, which invokes that these features are adaptations to high altitude tropical environments.

All of these morphological features paint the picture of an extreme environment, which has been described by Karl Hedberg, a Swedish botanist, as “summer every day, winter every night”.  As all of these mountains are located within 1000km of the equator, the environmental fluctuations occur daily instead of seasonally, with every day being warm and every evening being cold with nightly frost.

Figure 3. A population of giant senecios on the third highest and most ascended peak of Mt. Kenya, Lenana.

The article, titled “Chloroplast DNA variation and the recent radiation of the giant senecios (Asteraceae) on the tall mountains of eastern Africa” (Knox & Palmer, 1995. PNAS Vol. 92. pp. 10349-10353) challenged the common dogma that the ancestors of the Dendrosenecio lived at low altitudes allowing them to migrate in the lowlands of the region and that the current distribution reflects parallel evolution on each mountain.  The authors joke that this train of thought is very anthropo-centric because humans are obliged to live at lower altitudes and climb mountains one at a time and therefore expect plants to do the same.  They invoke that long-distance dispersal is more likely than migration and that it is possible for colonists to have started near the top and evolved their way down a mountain.  To explore this hypothesis, they look at the family relationships (phylogeny) between 11 species within the Dendrosenecio by analysing chloroplast DNA. 

The authors found 60 mutations among the 11 species that were informative regarding the relationships between the species.  Their results indicate that the giant senecios are an isolated lineage relative to the greater Senecioneae clade, with few molecular similarities to their closest relatives.  Furthermore, they believe that it could be possible that other high-altitude tropical Senecioneae around the world may be more closely related.  They go on to compare the Dendrosenecio with other giant-rosette plants in the Asteraceae (the larger group that Senecioneae falls within) and found little difference and found that across the world, a consistent feature of these plants was the radical morphological divergence from their closest known relatives. 

The heart of this article is the discussion on the radiation of the Dendrosenecio.  Their results indicate that Dendrosenecio originated in Tanzania, in eastern Africa, at high-altitude on Mt. Kilimanjaro and that the subspecies D. kilimanjari subsp. kilimanjari and D. kilimanjari subsp. johnstonii evolved via a downward altitudinal radiation, with a long distance dispersal event giving rise to D. meruensis on Mt. Meru.  The recent ages of the mountains that the giant senecios inhabit indicate that the radiation of Dendrosenecio occurred within the last one million years.  The non-Tanzanian giant senecios can then be sub-divided into 3 clades: a Mt. Kenya/Aberdares sub-clade, a Western Rift Zone/Mt. Elgon sub-clade and the Cherangani Hills sub-clade. 

Figure 4. The phylogeny of Dendrosenecio species and their geographical locations.

In general, the molecular data indicates that the diversification of the giant senecios involved repeated altitudinal radiation – meaning once a mountain had been colonised, species would diversify within the altitudinal ranges available to them, moving mostly down, but also up the mountain slopes.  Importantly, there was no evidence found to suggest that they had colonised mountains from a lowland ancestor, further invoking the theory of many long-distance dispersal events.

The biogeographic component shows that, as one would expect, species on neighbouring mountains are more closely related than species on farther off mountains, with just one exception.  Interestingly, there was no evidence found of recent establishment of one species that another species currently inhabited, indicating that habitats need to be unoccupied for successful colonisation.

This article outlines the basic trends of diversification of the remarkable genus Dendrosenecio and how they came to populate the mountain tops of east Africa’s tropical peaks.  I truly hope that one day I’ll be able to visit these amazing plants.  I just hope that it’s on an all-expenses paid working field trip. 

Altitude as an Ecological Tool

This month I’ve chosen to look at an article that is more relevant to my ongoing research this year by discussing a paper titled: “The use of ‘altitude’ in ecological research” by Christian Kömer, 2007 (TREE: 22 (11): 569-574).

This article is about the confusion in the scientific literature regarding altitude phenomena – namely ecological and evolutionary responses of biota to geophysical influences.  About ¼ of the Earth’s land surface is covered by mountains, where about 1/3 of terrestrial plant species diversity is endemic and supply half of the human population with water.  Furthermore, mountains offer steep environmental gradients, creating a great opportunity for biological research – particularly for exploring evolutionary adaptation over short spatial distances.

The author of this opinion article stresses to point out that many researchers have made the mistake of interpreting results that often include unique local conditions, such as fire, land use or drought that are not generally associated with altitude above sea level.  In reality, many findings that report supposed mechanisms that influence biota from different altitudinal gradients are in fact confusion between other environmental drivers that have been put under the umbrella term ‘altitude’.

Science strives to make over-arching blanket theories to explain observations or phenomena in order to simplify our understanding of the natural world.  Attempts have been made to correlate altitude with reduction of species, productivity, body or organ size, physiological and morphological trait trends or gene-ecological and life-history characteristics.  Seemingly altitude phenomena are particularly difficult to distil into a general, global altitude-related theory of biological phenomena because of many confounding variables, such as variable moisture gradients that occur along altitude gradients.  This article attempts to clearly distinguish those variables that change with altitude (e.g. atmospheric pressure and temperature) and those that do not (e.g. moisture and wind).

I find this article particularly interesting, as my current research project is attempting to ascertain the underlying causes of the high mortality rates of the Clanwilliam cedar (Widdringtonia cedarbergensis) in the Cederberg Mountains.  I am expecting that there will be a link between higher mortalities and higher temperatures and lower moisture availability across its range.  This article stresses that I will need to be careful when analysing the relationship between altitude and moisture availability as there is no global trend.  However, temperature is a variable that is physically tied to altitude giving me confidence in correlating these factors.

The primary global geophysical change with altitude is the decrease in land area with increasing altitude.  This seems rather obvious, but it is important for science to define such relationships.  This is a particularly interesting trend, because available land area has a major influence on biotic diversity and evolution.  Above the altitudinal tree limit (which varies around the world), on average, every increase of altitude by 167m results in a halved land area.  This average varies between mountain ranges.

Figure 1. The pattern in the European Alps of land area per 100m steps above sea level (a.s.l) starting from 1500m a.s.l.  

This figure clearly illustrates how land area consistently decreases with increasing altitude.  In the Alps an average of 150m of altitude results in half the amount of land area.

Along with the altitudinal loss of land area, there are 4 primary atmospheric changes associated with altitude:

1.       Atmospheric pressure declines for every kilometre gained in altitude with some regional trends although the general pattern is global.  This has an impact on respiration in animals and gas exchange in plants due to the reduced partial pressure of gases such as CO₂ and O₂.  This has allowed for interesting adaptations, such as more efficient CO₂ fixation in plants and more porous egg shells in birds to facilitate higher rates of O₂ diffusion to the embryo.

2.       Air temperature drops by 5.5 degrees Kelvin per kilometre of altitude on average.  Many plants have learnt to adapt to this by decoupling themselves from free convection and the ambient temperatures, allowing them to warm significantly under solar radiation, creating stable conditions for photosynthesis.  However, there is no global trend for all plant’s departures from ambient conditions and local and/or life form-specific patterns are likely to govern the degree of departure.  Instead, there is a trend seen in low-stature vegetation (e.g. cushion plants) of all mountains, where a thermal contrast is apparent in high altitude vegetation.  Furthermore, tall plants (trees) generally exhibit similar altitudinal reductions in temperature as the atmosphere does, which helps to explain the uniform position of tree lines that are restricted by a common isotherm of the mean temperature during the growing season (between 6˚C and 7˚C)(see Figure 2).  Due to these differences among organisms, the author points out that in order for altitudinal thermal gradient analyses to be biologically meaningful, only the temperatures that are physiologically effective need to be considered.

      Figure 2.  A photograph of the mountain tree-line in at Banf National Park, USA. 

3.       & 4. For both solar and UV-B radiation, the actual amount and effect has been misrepresented.  In both cases, the effects of clouds and fog mitigating radiation have not been considered.  For solar radiation, under a clear-sky profile only, solar radiation increases with altitude, but this is never realised due to effect of clouds and fog.  UV-B radiation contributes a higher fraction at any given solar radiation with increasing altitude.  Again, however, clouds and fog mitigate this effect.  At peak solar radiation, there is a consistent increasing global trend of increasing UV-B radiation with altitude, but this is not seen in mean daily or seasonal trends.

  

Perhaps the most important part to this article is the climatic trends that are not generally related to altitude.  The most important thing to note for all of these variables is that there are no clear global altitudinal phenomena for precipitation, wind velocity or seasonality.  The importance of this cannot be understated, as it is a far worse mistake to attribute a false causational variable to a pattern than to mistakenly not attribute a (true) causational variable to a pattern.

In conclusion, the importance of this article can be seen in the potential consequences of misusing altitude and its associated variables as an ecological tool.  In the case of my research project, if I was to falsely assume that moisture availability was to decrease with increasing altitude, this information could potentially be used in replanting efforts.  These efforts would be likely to fail, as it far more likely that the cedar trees rely on micro-climates between and on rocky outcrops than on particular altitudinal-moisture trends, even if this the general trend.  As Kömer (2007) notes, because there is no ‘standard mountain’ any data collected along altitudinal gradients will reflect a combination of the regional peculiarities and general altitude phenomena.

Conservation Successes (BIO4000/1)

This month I’ve decided to focus on a more conservation orientated article to really sink my teeth into.  The article I’ve chosen is titled: “Conservation successes at micro-, meso- and macroscales” (2011 TREE 26(11):585-594).

This article from the journal Trends in Ecology and Evolution reviews the success stories in conservation around the world.  It tries to lay a platform of past successes at different scales to promote future conservation triumphs.  Focus is placed on the different scales at which conservation efforts are focused.  The three scales used in this article are micro-, meso- and macro-scale. 

MICRO-SCALE

Micro-scale conservation projects are emphasised by the preservation of habitat and species.  Protected Areas (PAs) are the keystone behind these conservation initiatives, where vulnerable habitats and endangered species can be preserved.  This scale of conservation is the launching point of localised efforts and has obtained success around the globe.  Unfortunately, a lot of responsibility falls onto the PAs and often the conservation of habitats and species are not realised, due to ineffective management, lack of funding and many other reasons.  However, it isn’t all doom and gloom.  In Brazilian Amazonia, the largest remaining area of tropical rainforest, PAs have significantly reduced habitat loss by deforestation, with an estimated 37% of the decline in yearly deforestation rates in Brazil between 2002 and 2009 attributed to the preservation of forest in newly established PAs. 

The figure above shows how the rate of deforestation in Brazilian Amazon has greatly decreased between 2002, where it was at a decadal peak, to 2009 where it is at a 20-year low.  This has been largely attributed to the establishment of new PAs. (Source: 2011 TREE 26(11):585-594)

Habitat protection via the use of PAs is not the be-all-and-end-all of conservation at the micro-scale.  Often, major interventions are required to properly conserve habitat and species.  These interventions include rehabilitation, reforestation, reintroduction, population augmentation and the eradication of invasive species. 

A further conservation method at the micro-scale is to maintain ecosystem services.  This is something that I’m particularly interested in, as I often get disillusioned with conservation efforts that focus on a single species for mostly sentimental reasons, such as large cats.  I feel efforts to conserve should be at the ecosystem-level, because habitat and species fall within this scope.  Once an ecosystem is conserved, its services as an ecosystem, such as carbon sequestration or water filtering, can be maintained.  The ecosystem can then support the habitats and species within it. 

Luckily, awareness is growing that human’s livelihood and welfare is strongly linked to the health of our ecosystems.  In Madagascar, deforestation of upland forests caused stream siltation and lowered water yields required by lowland farmers.  The potential consequences of further deforestation and effects on the hydrology cycle of the forest was enough to convince the locals and Malagasy Government to commit to tripling the area of protected forests in the country. 

I often grapple with the complexities of trying to sell an idea to someone.  However, in the case of micro-scale conservation, I feel the method is clear.  In the Madagascar example, instead of trying to convince the locals or government of the importance of conserving the habitat (forest) and species (trees, lemurs, etc.), an ultimatum of sorts can be presented.  Without the ecosystem services that the forest and plants and animals within it provide, the livelihoods and welfare of the people of the region and country are at risk.  Once persons feel threatened, they are more likely to respond.

A slightly different approach at the micro-scale is to commoditise the specie or species at risk.  In the Western Cape of South Africa, fynbos (the predominant vegetation type of the region) flowers are sustainably harvested to subsidise conservation costs.

In short, conservation at the micro-scale relies heavily on support from local residents.  This can be done by creating an incentive, instead of a barrier for the conservation of a habitat or species.

MESO-SCALE

At the meso-scale, efforts that primarily include trans-boundary conservation agreements and the international regulation of illegal wildlife trade are required to protect biodiversity at the regional-level. 

Animals with expansive ranges that often extend beyond the arbitrary boundaries of country borders are in particular need of collaborative efforts between countries.   PAs in different countries can be joined with migration corridors for large-bodied animals, such as elephants and gorillas. 

A major threat to biodiversity in the world is the international trade in wildlife.  Meso-scale conservation efforts can prove to be a major thwarter of this illegal trade.  An example of this is evident in the illegal trade of tiger body parts that are used in Asian medicine.  A regional agreement by the Association of Southeast Asian Nations (ASEAN) Wildlife Enforcement Network which aims at sharing information on wildlife crime is reducing the smuggling of tigers across borders. 

Bald eagles (a) and golden lion tamarins (b) - 2 iconic species rescued from the brink of extinction. (Source: 2011 TREE 26(11):585-594)

MACRO-SCALE

Macro-scale conservation aims at limiting unsustainable business practices that negatively affect biodiversity.  Because it is at the macro-scale, multinational corporations are the major culprits.  Multinationals, such as Nike and Walmart, are now the major drivers of habitat loss and overharvesting in many developing countries.  The solution to this often comes in the form of public pressure (via boycotts of products) by consumers in developed countries, to force a change in the multinational’s practise in the developing world.

Global organisations such as the UN Climate Change Summit set up goals.  For example in Cancun, Mexico, the Board of Consumer Goods announced a goal to achieve zero deforestation in products such as beef, palm oil, paper and soya by 2020.  With technological advances, such as the use of satellite imagery, these goals can be monitored and verified by independent bodies. 

The use of laws is also essential to macro-scale conservation.  For example, multinational banks, such as Citigroup, have decided not to sanction loans to dodgy forestry projects and to require rigorous verification of eco-certification.  I personally have quite a radical view on the relationship between law and nature.  I feel anything that is part of the Earth: animals, plants, mountains and rivers and the ecosystems they form part of should be given juristic rights in much the same way that multinational corporations are given rights.  In this way, their unhindered exploitation would be deemed unlawful.  I strongly recommend reading Wild Law written by Cormac Cullinan, a South African environmental lawyer, for more on this topic.

Although this article focusses on the success stories of conservation, as the authors point out, more conservation projects fail than succeed.  The beauty of this article is the inspiring and optimistic outlook of the authors; they hope to engender hope in conservationists to continue their hard-fought work.  I am certainly optimistic that the tide is changing.  The battle between conservation and exploitation will slowly become a level-footed playing field.  With further awareness and education of the perils of unhindered exploitation, conservation’s hard, sustainably-farmed-and-crafted, leather boot will be firmly jammed in the door. 

Pollination Problems (BIO4000/1)

The first article that caught my eye was related to pollination and its intrinsic link to plant biodiversity.  Ecology and, more specifically, pollination biology is one of my major interests, so it stuck out above most of the genetics, biochemistry or microbiology articles that frequent many popular science journals.  

(Photograph taken in Nieuwoudtville, Northern Cape)

This article, authored by Anton Pauw from Stellenbosch University is titled: “Can pollination niches facilitate plant coexistence” (2013 Trends in Ecology and Evolution 28 (1): 30-37) and has the potential to help us better understand the conservation requirements and ecology of the Cape Floristic Region’s pollinators and plants, with potential implications for the Western Cape’s eco-tourism and fruit cultivation. 

Pauw is trying to find out why there are so many plant species on Earth.  This article, therefore, focuses on an explanation for the origin of plant species and an explanation for how they can coexist.  There are many ways plants can evolve and speciate [become a unique species] and Pauw is looking specifically at the roles pollination and pollinators play in it [Pollination: the transfer of pollen from the anther (man-bits) to the stigma (lady-bits); Pollinator: an animal that carries the pollen between flowers].   Changes in pollinator are said to be associated with 25% of speciation events in plants and is therefore responsible for a great amount of our plant diversity. 

Pollinator-driven speciation creates species that are different in their floral features.  For example, a change in the structure of a single-scent molecule in the nectar can result in speciation if the different scent attracts a novel pollinator. The broader question here is: “In the absence of other differences, are species with different flowers able to coexist from an ecological perspective?” 

The article revolves around Niche Theory, which says coexistence is possible if intraspecific (within a species) competition is stronger than interspecific (among species) competition.  This expects that each species limits its own abundance rather than be limited by the abundance of competing species.

Species generally limit their own abundance by using all of a resource, and so the number of limiting resources determines the number of species in a community of plants.  If a plant only has one specific pollinator, then it can become a limiting resource, if the likelihood of a flower being pollinated decreases with increasing density of flowers from the same species, which means it would produce less seeds and have fewer offspring.  This scenario would allow for a mutant or alien invasive plant, which uses a different pollinator (or pollinator resource) to invade the community and coexist with the resident plants.  

A good example of this could be in a monoculture (only one species in the plant community) of a bird-pollinated species, the amount of seeds the plants can produce may be limited by pollen transfer when there are lots of flowers in the area if the birds become satiated and they do not visit every flower, so some don’t get pollinated.  This monoculture could then be invaded by an insect pollinated species, which won’t have this same limitation.  The two plant species can then have separate pollination niches.

Seven tests can be used to see if niche theory, driven by pollinator speciation, is at play.  The article runs through these seven tests and the theoretical and practical answers to them.  From an exploration of current literature and studies, it can be concluded that the jury is still out on whether or not separation of pollinators can allow plant species to coexist.  Firstly, evidence is mounting that the amount a flower or plant is pollinated declines with an increase in the density of flowers from the same species.  Secondly, further evidence suggests that a decline in the amount a flower is pollinated can decrease the growth of the total plant population.  Although no studies have yet linked these two mechanisms to show that competition within the same species for a pollinator can lead to the regulation and stabilisation of the density of a plant population. 

This study links neatly in with conservational issues.  A deeper understanding of the roles of pollinators in promoting plants species coexistence is required from a pure academic perspective, but it can be crucial in showing the possible effects of human influences (which is generally disruptive) on pollination and on the diversity of pollinators. 

If pollinators are, in fact, a limiting resource for plant species, then a decline in their diversity can shrink the potential niche space, most likely creating a domino-effect leading to decreased plant diversity.  The potential effects of this are far-reaching and are not just trivial academic banter.      

(Photograph taken on Table Mountain, Cape Town)

The Western Cape of South Africa contains one of the biodiversity hotspots in the world, The Cape Floristic Region (CFR).  It is the smallest of the six recognised floral kingdoms and contains a disproportionately high amount of diversity and endemism (meaning it occurs nowhere else on the planet).  There are more than 9000 vascular plant species of which 69% are endemic.  So our fynbos, which contributes to most of this diversity and endemism, is well worth looking after.  Not only is at extraordinary floral marvel, but monetary worth of fynbos biodiversity, due to harvests of fynbos products (e.g. wildflowers, honey) and eco-tourism is estimated to around R77 million per year.  So it is clear that the CFR has both an economic and biological value.

The fair Cape that I live in is also a major producer of fruit for the domestic and international market.  The sheltered valleys between the mountains are ideal for the cultivation of export quality fruits.  This includes your apples, grapes (and our delicious wine), olives, peaches and those juicy oranges.  The disturbance caused by farmers and all others to these regions has the potential do disrupt pollinator populations, which could then have a negative feedback to our export quality fruits. 

So by gaining a greater insight into the roles pollinators play in plant species coexistence and their greater ecological role, particularly in the Western Cape, it will allow us to lay down the theoretical understanding that is necessary to implement the practical conservation in this region.

Hello

Hello.  My name is Joseph Douglas Mandla White.  I am 23 years old and a keen botanist/ecologist.  This year I am studying Honours in Biological Sciences at UCT.  To further inspire and stimulate my own relationship with science, I will have a blog.  This blog will be aimed at those who have an interest and love for science (in particular botany and ecology), but maybe don’t have the understanding or access to explore it further.  

Each post will attempt at reporting and communicating what is going on in the world of science.  I will read a popular, current, peer-reviewed article from one of the more reputable science journals out there and give you the good bits that I hope you may find interesting and/or stimulating.   I will write a new post once a month for more or less the duration of the year, so there’s plenty of time for some interesting articles to pop-up.  

I will try to focus on conservation issues throughout my posts, either about South Africa or that can apply to South Africa.  I will also include photographs that I have taken on my travels and adventures that are related to each post and some that won’t be at all.  Happy reading, see you in the mountains.

Photograph taken in Kirstenbosch Gardens, Cape Town, South Africa.