Evolutionary transitions to disparate light environments: approaching a genomics-collections rapport

Transcription

1 Evolutionary transitions to disparate light environments: approaching a genomics-collections rapport Simon Tierney Hawkesbury Institute for the Environment Christian Ziegler photography

2 Evolution of Vision Arrived late but had immediate impact The light-switch hypothesis eyes a catalyst for the Cambrian Explosion Tracking phenotypic and genotypic changes to altered light environments to understand factors that drive adaptive radiations LIGHTS OFF - nocturnal bees - subterranean beetles - vision genetics/genomics - archival requirements from an invertebrate perspective

3 Research Connexions Behaviour, Ecology, Genetics & Vision Evolutionary transitions in behaviour - solitary to group living - diurnal to nocturnal foraging Facultatively Social Insects allodapine reed bees,, halictine sweat bees & polistine paper wasps van Gogh Wheat Field with Cypresses 1889 Sam Droege van Gogh Starry Night 1889 Allodapini Mike Schwarz Laurence Packer Augochlorini Therany Gonzales

4 Research Connexions Evolutionary transitions in behaviour - solitary to group living - diurnal to nocturnal foraging Behaviour, Ecology, Genetics & Vision Evolutionary transitions in light environment - daylight to dim-light > bees - surface to cave > diving water beetles Chris Watts Therany Gonzales

5 Research Connexions

6 Nocturnal Bees More common than you might think - obligate in 4 bee families Apoidea cladogram Convergent Phenotypes - enlarged compound eyes & ocelli - larger body size - wings resemble smaller species large stigma, low aspect ratio & loadingg Michener 2007 Body length Buchmann diurnal nocturnal Houston 1975

7 Nocturnal Bees

8 Nocturnal Bees Photic Niche Transition diurnal --> dim-light Comparative Phylogenetic Reconstruction diurnal + nocturnal spp. functional + phylogenetically informative genes Photoreceptor Protein Evolution search for molecular signal of behavioural transition Q: Are photoreceptor genes under adaptive selection?

9 Opsin Photoreceptor Genes Land & Nilsson 2002 Opsin-based Phototransduction Common Metazoan Ancestor conserved gene photopigment 11-cis-Retinal chromophore + Opsin Metazoa Eumetazoa Bilateria Plachetski et al Proc. R. Soc. B 277 Spectral Tuning Point mutations - red / green colour blindness Gene duplication - arthropods Rhabdomeric filters - butterflies

10 Functional Phylogenetics Putative Functional Mutation long-wavelength opsin Engel Tierney et al. 2012

11 Tracking phenotypic and genotypic changes to altered light environments to understand factors that drive adaptive radiations LIGHTS OFF - nocturnal bees - subterranean beetles - vision genomics - archival requirements Plato's Allegory of the Cave by Jan Saenredam, according to Cornelis van Haarlem, 1604, Albertina, Vienna. c/o British Museum

12 Subterranean Beetles Habitat transition driven by climate change via contraction of surface water bodies - Oligocene-Miocene aridification Mya large freshwater lakes still in central Australia > Australia drifts north to meet subtropical High Pressure band > Antarctic ice increase & sea level decrease > seasonal aridity - Late Pliocene aridifciation 3 Mya - present > increasing Antarctic ice cover > bumps high pressure cells further north to centre of continent > major aridification of 2/3 of Australia Fujioka & Chappell 2010

13 Subterranean Beetles Diverse species radiations - Stygofauna are now trapped within discrete calcrete aquifer pockets species from two sister tribes (Bidessini and Hydroporini) Surface Subterranean cave-dwelling animals live in ground water dark-adapted Convergent Phenotypes - regressed vision = essentially blind - pale exoskeletons - wingless Parallel eye regression - Enables investigations of regressive at an unheralded comparative scale

14 Subterranean Beetles Photic Niche Transition surface water --> aphotic ground water Targeted 60 functional genes photoreceptor & eye pigment Hybrid-capture approach transcriptomes of 5 spp to design RNA baits capture DNA of ~ 40 spp Sequenced on high-throughput platform Q: What are the genetic mechanisms of regression? Neutral or selective pressures?

15 Subterranean Beetles Early results show: photopigment 1. Loss of opsin expression coincides with pseudogene mutations > evidence for neutral mechanisms 2. Pseudogene mutations present in descendent taxa > evidence for speciation in situ 3. Technical problems - questions reliance on transcriptomes alone > probable sequencing contamination > some assembly errors

16 Rapport Tracking phenotypic and genotypic changes to altered light environments to understand factors that drive adaptive radiations LIGHTS OFF - nocturnal bees - subterranean beetles - vision genomics - archival requirements 1998

17 Archival Requirements From an invertebrate biologists perspective Existing dry collection pinned specimens - useful for phenotypic investigations - fragmented degraded DNA > Sanger barcoding & Ancient DNA techniques applied with limitations Wish list of preservation - DNA stabilisation > Ethanol - RNA stabilisation > rapid permeation of tissue cells - frozen minus 20C > covers all bases - meta-preservation e.g. bees, vegetation collected from, pollen from scopal hairs & brood cells M. Nash Droege Rockwood Beekepers

18 Acknowledgements Reed Bees Schwarz Lab Funding Australian Research Council Flinders University Sweat Bees Wcislo Lab Funding Smithsonian Institution DC + STRI National Geographic Society Royal Entomological Society Healthy Bees Cook, Power, Riegler, Rymer, Singh Labs Funding Hort Innovations Western Sydney University Blind Beetles Austin, Cooper, Humphreys Labs Funding Australian Research Council University of Adelaide SA & WA Museums