Sunday, November 29, 2015

Meeting 1 dec: Can invertebrates have personalities?

Posted by Jessica Abbot on behalf of Alexander Hegg

This is an interesting essay on the topic of animal personalities, published last year in Animal Behaviour. Most personality studies have focused on vertebrates, but here the authors point out the possible advantages of studying personality variation in invertebrates. What are your thoughts on this? I think it would be an interesting topic to discuss at the next lab meeting.

Link: doi:10.1016/j.anbehav.2014.02.016

Title: Studying personality variation in invertebrates: why bother?

Abstract: Research on animal personality variation has been burgeoning in the last 20 years but surprisingly few studies have investigated personalities in invertebrate species although they make up 98% of all animal species. Such lack of invertebrate studies might be due to a traditional belief that invertebrates are just ‘minirobots’. Lately, studies highlighting personality differences in a range of invertebrate species have challenged this idea. However, the number of invertebrate species investigated still contrasts markedly with the effort that has been made studying vertebrates, which represent only a single subphylum. We describe how investigating proximate, evolutionary and ecological correlates of personality variation in invertebrates may broaden our understanding of personality variation in general. In our opinion, personality studies on invertebrates are much needed, because invertebrates exhibit a range of aspects in their life histories, social and sexual behaviours that are extremely rare or absent in most studied vertebrates, but that offer new avenues for personality research. Examples are complete metamorphosis, male emasculation during copulation, asexual reproduction, eusociality and parasitism. Further invertebrate personality studies could enable a comparative approach to unravel how past selective forces have driven the evolution of personality differences. Finally, we point out the advantages of studying personality variation in many invertebrate species, such as easier access to relevant data on proximate and ultimate factors, arising from easy maintenance, fast life cycles and short generation times.

Friday, November 20, 2015

Meeting Nov 24th: sex-bias, X-linkage, and rates of evolution

Posted by Jessica Abbott

D. melanogaster. Photo by Qinyang Li.
Although a number of members of the group are currently away, I thought it would be nice to have a meeting next week anyway. I don't think anyone else has planned anything, so I figured I might as well take the initiative. I suggest that we read the following short paper on the "faster-X effect" - how sex-biased gene expression and X-linkage affect rates of evolution.

Title: The effects of sex-biased gene expression and X-linkage on rates of adaptive protein sequence evolution in Drosophila

Abstract: A faster rate of adaptive evolution of X-linked genes compared with autosomal genes may be caused by the fixation of new recessive or partially recessive advantageous mutations (the Faster-X effect). This effect is expected to be largest for mutations that affect only male fitness and absent for mutations that affect only female fitness. We tested these predictions in Drosophila melanogaster by using genes with different levels of sex-biased expression and by estimating the extent of adaptive evolution of non-synonymous mutations from polymorphism and divergence data. We detected both a Faster-X effect and an effect of male-biased gene expression. There was no evidence for a strong association between the two effects—modest levels of male-biased gene expression increased the rate of adaptive evolution on both the autosomes and the X chromosome, but a Faster-X effect occurred for both unbiased genes and female-biased genes. The rate of genetic recombination did not influence the magnitude of the Faster-X effect, ruling out the possibility that it reflects less Hill–Robertson interference for X-linked genes.

Thursday, November 5, 2015

Lab meeting on November 10th at 10.00 on Phylogeography of marine animals

Next Tuesday I'll tell you a little about my past PhD-project in Helsinki University. Fika included, see you there!

My thesis in nutshell:
Phylogeography of amphi-boreal marine fauna

The Northern Atlantic and Pacific Oceans share a faunal element consisting of pairs of closely related vicariant taxa, known as the amphi-boreal fauna. The inter-oceanic systematic affinities reflect a history of shared ancestry since dispersal through the Bering Strait and across the Arctic basin, which was initiated by the opening of the Bering Strait at the end of the Miocene. In my PhD I examined the dynamics and consequences of the faunal interchange between the Atlantic and Pacific Oceans since that time up to the present. This was done by comparing differences in the mitochondrial gene sequence variation in different taxonomic groups and across the circum-boreal geographical scale, comprising both newly produced sequences and data from literature, from altogether 70 species or species groups (molluscs, crustaceans, echinoderms, polychaetes, fishes and mammals). Two exemplary genera, pelagic fish genus Clupea and boreal-arctic bivalve Hiatella were examined more closely and with additional markers.

The phylogeographical histories of the Pacific–Atlantic amphi-boreal taxa were found to be remarkably variable. A simple vicariant history since an early, Pliocene or Early Pleistocene (6–3 My ago) dispersal was inferred only in about half of the examined taxa, whereas signatures of more than one trans-Arctic dispersal were found in a third of the cases. A close inter-oceanic relationship that would reflect recent trans-Arctic dispersal or ongoing gene flow was found to be common for amphi-boreal genera (40% of cases). Overall the estimates of inter-oceanic mitochondrial divergence within each of the broader taxonomic groups varied greatly, up to 10–20 fold, and suggest that trans-Arctic faunal dispersal has been a repeated process through the time frame considered. Based on the molecular divergence, several instances of putative new allopatric species were detected in the invertebrates.

Repeated trans-Arctic invasions have practically always resulted in secondary contacts of diverged lineages (for this data, in all cases but one). The Pacific herring C. pallasii, of East Asian origin, invaded the Northeast European seas post-glacially and then differentiated into separate regional populations. In Europe, hybridization with the native sister species C. harengus, the Atlantic herring, has also taken place. The amount of introgression from the Atlantic to the Pacific herring was variable between the various contact regions of the taxa. Most heavily introgressed fjord population in northern Norway has parallels in the boreal bivalves Macoma and Mytilus, for which similar repeated invasion history has been inferred.