Curator of Arachnids & Myriapods
My research focuses on understanding general patterns of diversification by examining how novel traits evolve, function, and relate to biogeography patterns. My research integrates between questions in evolution, such as diversification of novel traits and ancient biogeography patterns, to more organismal-based approaches in the field of arachnology, such as taxonomy and comparative morphology. The focus of my research thus far has been on palpimanoid spiders, which have restricted distributions, exhibit strikingly deviant morphological, behavioral, and ecological traits, and are ancient lineages with a fossil record. In particular, I am interested in how the evolution of novel modifications of the cephalic area and chelicerae allow them to capture prey in innovative ways. My research includes working with both living and extinct lineages, allowing for evolutionary hypotheses to be examined across time.
- Systematics and Taxonomy:
Using molecular and morphological data, my research seeks to understand evolutionary relationships among different palpimanoid spider lineages, both living and extinct, with a focus on pelican (Archaeidae) and trap-jaw (Mecysmaucheniidae) spiders. Knowledge of evolutionary relationships is fundamental to my research, as it provides a context for addressing broader questions. As part of my research, I have proposed phylogenetic hypotheses that have incorporated extinct lineages directly into the phylogeny as terminal tips. I also have a strong field component to my research, mostly through expeditions to areas in the Southern Hemisphere such as Madagascar, Chile and South Africa. Natural history observations, such as predatory and mating behaviors, often form the basis of my research questions. Major results from this research include taxonomic keys and revisions that document the world’s biodiversity, and phylogenetic hypotheses that have clarified higher-level and species-level relationships.
- Biogeography and Timing of Lineage Diversification:
My research examines biogeography patterns, with a specific interest in the Southern Hemisphere. To examine biogeographic hypotheses, I have experience performing analyses that estimate divergence times with fossils being used as both calibration points and as terminal tips. I also employ ancestral area reconstructions to examine biogeography patterns. Palpimanoid spiders are a model system for this type of research because of their restricted southern hemisphere distributions and low dispersal abilities. One finding from my research is that the estimated divergence time between northern hemisphere fossil taxa and southern hemisphere extant taxa is congruent with Pangean break-up into Laurasia and Gondwana in archaeid spiders. This work offers insight into the methodology of incorporating fossil taxa directly into divergence time estimation and biogeography analyses, particularly crucial when fossils occur in different areas than the extant lineages. I also have a specific interest in the evolution of Madagascar’s biota: for example, why do Madagascar archaeid spiders show greater rates of trait diversification and have higher levels of sympatry compared to closely related lineages in other parts of the world? This work suggests that ancient paleoendemics on Madagascar seem to have different diversification patterns compared to more recent neoendemics.
- Evolution of Novel Traits:
A goal of my research is to discover general patterns relating to how novel traits evolve and promote diversification. Using comparative phylogenetic methods, my research focuses on trait evolution in the palpimanoid spiders, which have evolved unique predatory strategies that directly relate to their unusual carapace/chelicerae morphologies. Using comparative methods I have found that, in archaeids, the highly specialized carapace/chelicerae morphology is significantly correlated with habitat and ecology. There is remarkable diversity in carapace/chelicerae morphology among archaeid species, particularly among Madagascan lineages, and this variation may allow species to co-exist in sympatry. Contrary to the typical pattern of explosive radiation among Madagascan neoendemics, Madagascan archaeids seem to have gradually accumulated trait diversity over long periods of time.
My research also focuses on the evolution of trap-jaw predatory behaviors in spiders. Animals have evolved numerous innovative ways to produce extremely rapid movements, overcoming biological constraints on muscle speed. Extremely fast trap-jaw movements have been described for several ant genera but were not known, prior to my dissertation research discovery, in the arachnids. Within the trap-jaw spider family, using high-speed recordings, I found that there is a great range of chelicerae closing speeds in mecysmaucheniids. Molecular phylogenetic analysis revealed that high-speed strikes in this spider family has evolved multiple times independently. This research will make important contributions to evolutionary biology by examining how novel structures and behaviors evolve.
- Comparative Functional Morphology:
Understanding patterns of trait diversification requires knowledge of the underlying function, particularly in the context of a highly integrated structure, such as a trap-jaw mechanism. However, trap-jaw mecysmaucheniids are millimeter sized, ranging in carapace length of 1-4 mm, making them difficult to dissect. My research uses novel techniques to overcome these size challenges: tomography scanning, by creating 3D computer models that can be “virtually dissected,” presents a means to gain detailed information about internal biological structures in even the smallest organisms. In collaboration with scientists at the Lawrence Berkeley National Lab synchrotron, we’ve scanned 35+ species of mecysmaucheniids and their close relatives, and these scans are used to visualize internal anatomy and create 3D computer models. Using these scans, I was able to identify the structural innovations that appear to have set the stage for evolution of high-speed trap-jaw mechanisms. Furthermore, I am currently using 3D computer models to perform morphometric analyses on different species of trap-jaw spiders. Morphometric analyses will allow me to address, from a phylogenetic context, hypotheses about rates of evolution in morphological structures and whether some lineages are more diverse than others.
I welcome collaborations focusing on similar questions that that bridge function, morphology, distribution, diversification and systematics. I encourage students and postdocs to contact me directly if you have an interest in this type of research, and/or in research focusing on arachnid systematics and classification.
Wood, Hannah M. 2017. Integrating fossil and extant lineages: an examination of morphological space through time (Araneae: Archaeidae). Journal of Arachnology, 45(1): 20-29. doi:10.1636/JoA-S-16-039.1
Wood, H.M., Parkinson, D.Y., Griswold, C.E., Gillespie, R.G. and Elias, D.O. 2016. Repeated Evolution of Power-Amplified Predatory Strikes in Trap-Jaw Spiders. Current Biology, 26(8): 1057-1061. doi:10.1016/j.cub.2016.02.029
Wood, H.M., Gillespie, R.G., Griswold, C.E., Wainwright, P.C. 2015. Why is Madagascar special? The extraordinarily slow evolution of pelican spiders (Araneae, Archaeidae). Evolution, 69: 462–481. doi:10.1111/evo.12578
Wood, H.M, Matzke, N.J., Gillespie, R.G., Griswold, C.E. 2013. Treating fossils as terminal taxa in divergence time estimation reveals ancient vicariance patterns in the Palpimanoidea spiders. Systematic Biology 62:264-284
Wood, H.M, Griswold, C.E., Gillespie, R.G. 2012. Phylogenetic placement of pelican spiders (Archaeidae, Araneae), with insight into evolution of the “neck” and predatory behaviors of the superfamily Palpimanoidea. Cladistics 28:598–626
Griswold, C., Wood, H.M., Carmichael, A. 2012. The lace web spiders (Araneae, Phyxelididae) of Madagascar: phylogeny, biogeography and taxonomy. Zoological Journal of the Linnean Society 164:728–810
Wood, H.M. 2008. A revision of the assassin spiders of the Eriauchenius gracilicollis group, a clade of spiders endemic to Madagascar (Araneae: Archaeidae). Zoological Journal of the Linnean Society 152:255-296
Wood, H.M., Griswold, C.E., Spicer, G.S. 2007. Phylogenetic relationships within an endemic group of Malagasy ‘assassin spiders’ (Araneae, Archaeidae): ancestral character reconstruction, convergent evolution and biogeography. Molecular Phylogenetics and Evolution 45:612-619
[ TOP ]