Evolution of Interactions

 

Evolution of Interactions

A Ficus craterostoma growing on/strangling a Monkey Thorn on campus. In its natural forest habitat in the archipelago of Afromontane forests, this strategy allows F. craterostoma to bear its fruit above the forest canopy.

 

WHAT

Interactions between genes, individuals and species determine how the cookie crumbles. The evolution of these interactions will therefore determine what we see. Jaco is mainly interested in what kinds of interactions selection would favour. However, interactions leave patterns in genetic variation and we have also used these patterns to infer the past. Jaco finds three scenarios especially fascinating and most of our work has been on these: 1) when individuals that interact are related and 2) when reproduction or 3) dispersal are involved. In fact, these problems can all be intertwined and affect each other's evolution.

 

HOW

Our research is interdisciplinary and we use techniques, tools and approaches from a variety of fields: Behavioural ecology, Evolutionary ecology, Population genetics, Molecular ecology, Statistics, Phylogenetics and Computer programming. Activities vary from counting female wasps to sequencing a genome.

 

STUDY ORGANISMS

We look at many aspects of the fig tree – fig wasp mutualism. It is a fantastic model for many academic and applied questions. We have also looked at the genetic history of Afrikaners, which is a novel South African opportunity that many Afrikaners find fascinating and that may help with building a South African identity. We are interested in host-parasite co-evolution and explored the biology of the nematode, Spirocerca lupi.

 

EXAMPLES

1. Female biases, fighting and dispersing fig wasps

We have shown that fig wasp mothers regulate the number of sons they produce very carefully in order to minimize competition between their sons. However, if competition between fig wasp males is too intense they will evolve robust morphologies and fighting behaviour to fight even with their brothers. In addition, they may adopt dispersing behaviours. In the figures below, two pollinator males of the genus Platyscapa are shown. The fighting P. awekei has more males per female driving selection for dispersal and fighting.

Figure. Two pollinator males from the genus Platyscapa. Left – Platyscapa awekei that has strong jaws and heads to fight with and long legs to disperse; right – Platyscapa soraria that has none of these


 

2. 350 years of almost no non-paternity in Afrikaners

A man inherits his father's Y-chromosome. Men with the same surname should thus have the same Y-chromosome. Any mismatch would indicate to an adoption or a cuckoldry event. We call these non-paternities, as the biological father did not raise the child. Matching Afrikaner genealogies and Y-chromosomes we found that less than a percent of Afrikaner children were non-paternities. Selection will thus favour paternal investment in offspring.

Figure. An Afrikaner genealogy with haplotypes indicated with colour. Most are simply the result of mutations, but the brown one (22.10) is a non-paternity.

 

3. Fragmentation affect fig trees differently

Fig trees are pollinated by fig wasp that can transport pollen over great distances. The record is 160 km far. As a result, fig trees growing in forests should be immune to the effects of fragmentation of the habitat because wasps could travel between forests. However, species' biology differ in ways that result in one species having very distinct populations whereas others' are hardly different.

 

Table. Showing the genetic difference measured in FST and F'ST between populations for three species in forests.

Ficus species

Global FST

 F'ST

AMOVA: percentage variation among populations

F. bizanae

0.12 (0.07-0.17)***

  1. 23
  1. 85

F. craterostoma

0.05 (0.01-0.09)***

  1. 16
  1. 25

F. sur

0.04 (0.03-0.05)***

  1. 11
  1. 89

***P<0.001

4. Afrikaner ancestry through genetics

Genealogies and private DNA tests show that Afrikaners (a human population in South Africa) are the result of admixture between European immigrants, slaves imported from Africa and Asia and local Khoisan. We genotyped 77 Afrikaners at 5 million SNPs to quantify the extent and nature of their admixture. The first surprise was a small but pervasive Khoisan ancestry. Only one marriage between an European and a Khoisan was recorded in the Cape, suggesting substantial gene flow between "trekboere" and Khoisan woman at the frontier. The second surprise was a substantial West, rather than East African signal. The great majority of slaves came from the East of Africa and it must have been the earlier arrival of West African slaves (4 generations) that created this pattern.

 

Figure. STRUCTURE plot of Afrikaners showing admixture with non-European populations.

 

WHO

Principal Investigator

 

 

 

 

Jaco Greeff

 

Current students

MSc

PhD

Karina Pentz

Anton Klingenberg

 

Jun-Yin Deng

 

Former Students

MSc

PhD

Gert Jansen van Vuuren

Plant Breeder, Link Seed, Greytown

Jason Pienaar

Assistant Professor, University of Alabama

Vinet Coetzee

Senior Lecturer, BGM, UP

Ronnie Nelson

Self-Employed, Induku, Sweden

Heike Koberstein

Data Coordinator, Pannar seed, Greytown

Zee Ahmed

Scientist and Curator, Florida Dept of Agric & Consumer Services

Nico Chung

Bioinformatics Analyst at Welgene Biotech, Taipei, Taiwan

Meike Kruger

Inside Sales Manager at Fisher Scientific, Khel Am Rhein, Germany

Beryl Flatela

Senior Scientist, Ampath

 

SELECTED OUTPUTS

Deng, J.-Y., van Noort, S., Compton, S.G., Chen, Y., Greeff J.M. 2020. The genetic consequences of habitat specificity for fig trees in southern African fragmented forests. Acta Oecologica 102: 103560.

Chung, N., Pienaar, J., Greeff, J.M. 2019. Evolutionary stable sex ratios with non-facultative male-eggs first sex allocation in fig wasps. Oikos 128, 859-868.

Greeff, .J.M., Reid, K., Gagjee, J.R., Clift, S.J., de Waal, P.J. 2018. Population genetic structure of the parasitic nematode Spirocerca lupi in South Africa. Veterinary Parasitology 258, 64-69.

Greeff, J.M. & Erasmus, J.C. 2015. Three hundred years of low non-paternity in a human population. Heredity 115, 396-404.

Ahmed, M.Z., Li, S.-J., Xue, X., Yin, X.-J., Re, S.-X., Jiggins, F.M., Greeff, J.M., Qiu, B.-L. 2015. The intracellular bacterium Wolbachia uses parasitoid wasps as phoretic vectors for efficient horizontal transmission. PLoS Pathogens 10(2): e1004672.

Greeff, J.M. & Erasmus, J.C. 2013. Appel Botha Cornelitz: the abc of a three hundred year old divorce case. Forensic Science International: Genetics 7, 550-554.

Greeff, J.M. & Newman D.K.V. 2011. Testing models of facultative sex ratio adjustment in the pollinating wasp Platyscapa awekei. Evolution 65, 203–219.

Warren, M., Robertson M.P. & Greeff, J.M. 2010. A comparative approach to understanding factors limiting abundance patterns and distributions in a fig tree- fig wasp mutualism. Ecography 33, 148-158.

Nelson, R.M. & Greeff, J.M. 2009. Evolution of the scale and manner of brother competition in pollinating fig wasps. Animal Behaviour 77, 693–700.

Published by Kishen Mahesh

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