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Cold-water corals increase habitat heterogeneity and enhance biodiversity in deep waters worldwide. Despite the recognition of their importance in the deep sea, limited data exist on the ecology and evolution of deep-water corals. The overarching goal of this dissertation research was to integrate molecular, morphological, and ecological data to understand the degree to which populations are connected, species are distributed, and communities are assembled in the deep (250-2500 m) Gulf of Mexico (GoM). Specifically, several hypotheses were tested regarding the roles of environmental variables, particularly depth, influencing population and community structure. Combining phylogenetic and population genetic approaches with ecological data enabled species delimitations of many taxa while demonstrating that deep-water populations and communities diverge over short bathymetric distances. It appears that population isolation, congeneric species replacement and changes in community composition occur rapidly with depth, and these changes are likely due to a combination of both dispersal limitation and adaptive divergence with depth. Local self-recruitment may also be strong within any one site. Furthermore, results suggest that evolutionary history and neutral dynamics play a critical role in octocoral community assembly in the deep sea. This dissertation not only contributes a substantial amount of evolutionary and ecological information on a poorly studied group of foundation species in the deep sea, this research has broader implications for aiding in efforts to protect these long-lived, foundation species from anthropogenic disturbances. / Biology

Climate has a demonstrable impact on species distributions, with changes in climatic oscillations often producing complex downstream effects due to species-specific tolerances to changes in temperature and precipitation. In general, barring physiological or environmental barriers, species are predicted to migrate polewards, and possibly also upwards in elevation, in response to general equatorial warming (Walther et al. 2002). A major challenge to substantiating this predicted relationship between temperature and distribution, especially for highly mobile or nomadic species, has been the lack of suitable techniques for tracking species distributions with sufficiently high resolution to assess for evidence of range shifts over decadal timescales. However, the recent rise in the volume and availability of citizen science data has demonstrated its strong potential as a tool for elucidating responses to environmental change on large temporal and spatial scales (Champion et al. 2018; Hurlbert & Liang 2012; Soroye et al. 2018). Here we assessed the strengths and weaknesses of three different citizen science datasets in addressing questions relating to historical range shifts in two butterfly species endemic to the eastern United States: the pipevine swallowtail (Battus philenor) and its Batesian mimic, the red-spotted purple (Limenitis arthemis astyanax). Motivated by the prediction that there would be a quantifiable northward latitudinal range shift in both B. philenor and L. a. astyanax in response to historical regional warming, we ultimately analyzed twenty-four years of observational survey data from the North American Butterfly Association and found evidence to suggest that, surprisingly, from 1998 to 2021, there is no indication of a directional range shift in either the model or its mimic. However, consistent with expectations from classic mimicry theory we found evidence of a tight historical correlation between the ranges of B. philenor and L. a. astyanax over the years surveyed. Furthermore, we found that the annual variance in the ratio of models to mimics is significantly lower at the model’s northern range limit than in other parts of its range. This suggests that phenological coupling between these two species is subject to more intense selection at the range edges and that climate-induced changes in phenology likely have stronger fitness consequences in areas where the model species, Battus philenor, is relatively rare. Taken together, our results support the potential of citizen science data as a powerful resource for tracking historical spatiotemporal changes in highly vagile insect populations, particularly in tracking patterns linked to the long-term effects of climate change.

Anurans exhibit remarkable variation in reproduction, even among closely related species, with consequences for behavior across multiple life stages. Phyllomedusid treefrogs include explosive-breeders and better studied prolonged-breeding species. As adults, the explosive breeders gather rarely, in huge numbers, for intensely concentrated reproductive activity. As embryos, they have faster development, less gelatinous egg clutches, and tougher egg capsules than prolonged breeders, but much lower escape-hatching success in snake attacks. I studied adult and embryo behavior in the explosive-breeding gliding treefrog, Agalychnis spurrelli. First, in Chapter 2 I combined long-term natural history observations and automated acoustic recordings with machine-learning analysis to describe the phenology and environmental predictors of explosive breeding. I found that breeding occurs up to 11 times per year during 1–2-day long reproductive events, from late May to mid-September. Reproductive activity is strongly associated with rainfall over the previous 48 hours, especially afternoon and evening rain. This analysis advances our understanding of explosive-breeding phenology in anurans and highlights the importance of fine-scale changes in environmental conditions for frog reproduction and conservation. In Chapter 3, I tested the long-standing and widely accepted hypothesis that an unusual “egg-kicking” behavior by non-amplexed male A. spurrelli functions as an antagonistic strategy to dislodge and kill competitors’ eggs. I recorded and analyzed videos from breeding aggregations to demonstrate that egg-kicking does not dislodge eggs, rejecting this hypothesis. Instead, I propose this behavior functions as part of an alternative reproductive tactic under highly male-skewed operational sex ratios. In Chapters 4 and 5, I tested two hypotheses about why A. spurrelli embryos have strikingly lower escape-hatching success in snake attacks, compared to the prolonged breeding A. callidryas. In Chapter 4, I assessed a hypothesized sensory constraint, testing if later development of vestibular mechanosensing could constrain the ability of A. spurrelli embryos to sense risk cues. I found that vestibular mechanosensory ability, measured by strength of the vestibulo-occular reflex, strongly predicts hatching responses to physical disturbance in A. spurrelli, as in A. callidryas, and that its developmental timing is similar in both species. This rejects the hypothesized constraint and indicates that some other aspect of their biology causes species differences in escape success. In Chapter 5, I compared the egg-clutch biomechanics of A. spurrelli and A. callidryas and used egg-transplant snake-predation experiments and simulated attacks on de-jellied and control A. spurrelli eggs to test the role of egg and clutch structure in mechanosensory-cued hatching. I found that species differences in clutch structure affect vibration biomechanics and thus the cues available to embryos, and transplantation into A. callidryas clutches improved A. spurrelli’s escape success. Moreover, removing their tough jelly capsule increased hatching attempts and eliminated hatching complications. Together, these experiments show how parentally-produced egg and clutch structures contribute to species differences in embryo behavior and the effectiveness of antipredator defenses. Overall, this research enhances our understanding of how mating systems can influence behavior at multiple life stages and demonstrates the value of integrative and comparative research in elucidating mechanisms that underly functionally important interspecific differences in behavior.