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Impact of climate change on the physiology and distribution of Eleutherodactylus portoricensis
(2019-12-12)
Global climate is changing at unprecedented rates, causing detrimental effects on vulnerable organisms and forcing them to cope with unfavorable conditions. Ectotherms often adapt to changing abiotic variables by altering their distribution ranges. Amphibians are known to alter their distribution because of rising temperatures. In Puerto Rico we have observed a range-shift to higher elevations in one species of direct-developing frog. Here we considered two species that occur sympatrically in part of their range at El Yunque tropical montane reserve. One species, Eleutherodactylus portoricensis, is presently limited to high elevations above 700 m.a.s.l., although it was previously found down to 400 m.a.s.l. Contrastingly, its congeneric E. coqui, can be found at all elevations (0-1,300 m.a.s.l.). Our objective was to characterize both species’ thermo-physiological profiles and question if the observed range-shift to higher elevations of E. portoricensis was associated to higher physiological sensitivity. We evaluated critical thermal minima and maxima, and thermal preference for three populations: E. portoricensis (850m), and low (180m) and highland (850m) E. coqui. We also evaluated dehydration stress during jumping performance by reducing 5% of their body mass using dry-air chambers. Lastly, we modeled E. portoricensis current and future distribution range under various scenarios of climate change. Our results show that E. portoricensis has a narrower thermal tolerance range and prefers lower temperatures when given a gradient. Also, E. portoricensis showed lower performance levels than E. coqui when dehydrated. Our results suggest that higher physiological sensitivity may explain elevational range contraction on this species. In addition, distribution models show a decrease in occurrence probability later this century in comparison to current projections. Our models also predict a range contraction towards higher elevations. This range shift would most likely result in the extirpation of most E. portoricensis populations. This research highlights the vulnerability of an endemic tree frog in Puerto Rico as a consequence of anthropogenic climate change and the urge to develop effective conservation efforts....
Physiological and immunological acclimation in corals differing in life-history traits: a field experiment
(2020-05-20)
Corals can exhibit much variability in life-history strategies. A proposed categorization recognizes competitive, stress-tolerant and weedy species. 'Competitive' corals invest more energy towards growth, 'stress-tolerant' towards maintenance and 'weedy' towards reproduction. While competitive corals are declining due to climate change and anthropogenic stressors, stress-tolerant and weedy are thriving. We performed a reciprocal transplant experiment between a degraded and a more pristine reef, and measured the physiological (Symbiodinium density, chlorophyll a concentration, protein concentration) and immunological (oxidative stress) response of the stresstolerant Pseudodiploria strigosa and Orbicella annularis, and the weedy Porites astreoides. Results indicate that the studied species can rapidly and successfully acclimate to local environmental conditions. Comparisons among species suggest that the physiological and immunological response in P. astreoides, P. strigosa and O. annularis are more influenced by species-specificity than by life-history strategy....
Exploring mechanisms of behavioral flexibility and individual specialization through the comparison of members of multiple subspecies of honey bees.
(2020-04-02)
In this thesis, we explore the cognitive basis for the emergence of individual foraging strategies (IFS) across multiple honey bee subspecies using Reversal Learning assays and Free-Flying foraging problems. In Chapter 1 ...
Deciphering the Epargyreus clarus (silver spotted skipper) wing patterning genes
(2020-05-20)
Butterfly wing patterns have captivated evolutionary and developmental biologists for decades because of their vast diversity. Studies have focused on the molecular basis of pattern variation in the Nymphalidae, with little effort put toward skippers, family Hesperiidae. This study had two aims: identify the presence of Wnt genes through ISH and pharmacological drug injections, and test differentially expressed genes in three developmental stages, between wing types, and between wing compartments of E. clarus using RNA-sequencing. I hypothesized, that a simple yet modular set of genes was involved in wing pattern development of the skipper, similar to that of nymphalid butterflies and that genes such as WntA and Ubx would be differentially expressed as in nymphalids. ISH confirmed the presence of two Wnt genes and RNA-seq provided evidence of differential expression, suggesting that the genes underlining wing pattern diversity are being shared between these two distantly related families....