1. Brain size evolution

Why brain size is so variable across vertebrates?  What makes some animals having larger brains than others? What limits evolutionary brain size enlargement? During my PhD, I studied these questions in cichlid fishes from Lake Tanganyika and pipefishes/seahorses using phylogenetic comparative methods.

I am particularly interested in brain-body allometry. In the second chapter of my PhD thesis, I reported that the slope of brain-body allometry within species (static allometry) is strongly conserved across 40 cichlid species, indicating that this parameter may be an important evolutionary constraints for brain size evolution.

I recently published a study of brain-body allometry at the across-vertebrate scale. I show that birds and mammals are exceptional for their shallow static allometric slopes compared to other groups. I further reveal that the breakdown of static allometries is related to the extension of fetal brain growth period. These results indicate that evolvability of ontogenetic processes plays an important role in macroevolution. This study stands as one of few examples where the consequence of evolutionary constraint and its mechanistic basis are shown together. The data we collected and curated are freely accessible and reusable from the Figshare repository. 

Brain–body evolutionary allometry of six vertebrate classes. a) Class-level brain–body allometries of six major vertebrate lineages are shown in different colours (x and y axes are in log10 scales). Points represent species means and unbroken lines are least square regressions accounting for phylogenetic relatedness among species. b) shows minimum convex polygons of the morphospace occupied by Actinopterygii (N=963), Amphibia (N=86), Aves (N=1902), Chondrichthyes (N=147), Mammalia (N=1409) and non-avian reptiles (Reptilia, N=79).

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GEOMETRIC MORPHOMETRICS applied to head morphology of the largest freshwater pipefish, Doryichthys boaja from Malaysia. Black bar on the top-left indicates 10 mm. Closed circles indicate so-called "landmarks" that are assigned to describe the shape of fish head as a set of x-y coordinates. This approach allows us to study shape with minimum information loss; size, scale and rotation, for comparison across individuals or wide range of species.

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PHOTOGRAMMETRY allows a quick and easy reconstruction of 3D surface image. The above image is a skull of Reindeer Rangifer tarandus reconstructed from c.a. 50 photos. By calibrating the image using the scale photographed together with the skull, we can estimate the volume of antler without physically measuring it at all.

2. PHENOMICs approach to the interface between micro and macroevolution

New tools to measure phenotype now bring us an exciting opportunity to compile massive amount of phenotypic data of high complexity with accuracy. However, applications of these techniques in biological questions are not as fully explored as genomic tools. I am currently running several projects that use large amount of phenotypic data acquired through new techniques.

My approaches are geometric morphometrics, an increasingly popular method to study morphology, and photogrammtery, a quick and cost-effective solution to construct beautiful object surface images. I then apply phylogenetic comparative methods to large amount of accurate phenotypic data, collected through these novel techniques, to understand the interplay between micro- and macroevolution.

I am studying evolution in antler morphology of the family Cervidae (deers) and wing morphology of the family Drosophilidae (flies) and Zygoptera (damselflies). My tentative goal in these projects is to understand the role of multivariate genetic constraints in adaptive evolution.

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