THE PHENOTYPIC FLEXIBILITY OF THERMOGENIC CAPACITY: FROM PHYSIOLOGICAL MECHANISM TO EVOLUTIONARY IMPLICATIONS

Individuals face many selection pressures that change throughout their lives. Phenotypic flexibility, the ability to flexibly and reversibly modify a trait value, is one way an individual can optimally match its phenotype to the prevailing environmental conditions. In this dissertation, I used juncos as a lens to understand the causes of variation in flexibility within physiological systems and among individuals. In my first chapter, I investigated how Dark-eyed Juncos (Junco hyemalis) alter mechanisms of heat production and heat conservation to cope with variation in ambient conditions. My results demonstrate the ability of birds to adjust thermoregulatory strategies in response to thermal cues and reveal that birds may combine multiple responses to meet the specific demands of their environment. To further explore the thermoregulatory strategies available to juncos, in my second chapter, I assess their potential use of non-shivering thermogenesis. My results indicate that muscular non-shivering thermogenesis is not an important mechanism of avian thermoregulation, potentially as a consequence of a tradeoff between the many demands placed on avian muscles. In my third chapter, I measured 20 additional physiological traits to explore the mechanistic basis of flexibility in complex phenotypes. I show that the relationships among traits contributing to whole-organism performance varied with the environmental context. Moreover, whole-organism flexibility in thermogenic performance was correlated with only a handful of subordinate phenotypes. In my fourth chapter, I identified drivers of variation in flexibility among juncos. To do this, I integrated measures of population genetic variation with assays of thermogenic performance and indices of environmental heterogeneity for individuals across the genus Junco. I find that native temperature heterogeneity correlates both with population genetic variation and the degree of thermogenic flexibility exhibited by an individual. In my fifth chapter, I present a review that considers the evolutionary implications of phenotypic flexibility and contrast those with developmental plasticity. I hypothesize that because these two processes experience selection distinctly, confer stability to populations differentially, and will likely evolve at different rates. Collectively, this work helps us understand the role of flexibility in adaptation and species’ resilience to environmental change

Full lifetime perspectives on the costs and benefits of lay date variation in tree swallows

Animals must balance various costs and benefits when deciding when to breed. The costs and benefits of breeding at different times have received much attention, but most studies have been limited to investigating short-term season-to-season fitness effects. However, breeding early, versus late, in a season may influence lifetime fitness over many years, trading off in complex ways across the breeder?s lifepan. In this study, we examined the complete life histories of 867 female tree swallows (Tachycineta bicolor) breeding in Ithaca, New York, between 2002 and 2016. Earlier breeders outperformed later breeders in short-term measures of reproductive output and offspring quality. Though there were weak indications that females paid long-term future survival costs for breeding early, lifetime fledgling output was markedly higher overall in early-breeding birds. Importantly, older females breeding later in the season did not experience compensating life-history advantages that suggested an alternative equal-fitness breeding strategy. Rather, most or all of the swallows appear to be breeding as early as they can, and differences in lay dates appear to be determined primarily by differences in individual quality or condition. Lay date had a significant repeatability across breeding attempts by the same female, and the first lay date of females fledged in our population was strongly influenced by the first lay date of their mothers, indicating the potential for ongoing selection on lay date. By examining performance over the entire lifespan of a large number of individuals, we were able to clarify the relationship between timing of breeding and fitness and gain new insight into the sources of variability in this important life history trait.Fil: Winkler, David Ward. Cornell University; Estados UnidosFil: Hallinger, Kelly K.. Cornell University; Estados UnidosFil: Pegan, Teresa M.. University of Michigan; Estados UnidosFil: Taff, Conor C.. Cornell University; Estados UnidosFil: Verhoeven, Mo A.. University of Groningen; Países BajosFil: Van Oordt, David Chang. Cornell University; Estados UnidosFil: Stager, Maria. University of Montana; Estados UnidosFil: Uehling, Jennifer J.. Cornell University; Estados UnidosFil: Vitousek, Maren N.. Cornell University; Estados UnidosFil: Andersen, Michael J.. University of New Mexico; Estados UnidosFil: Ardia, Daniel R.. Franklin & Marshall College; Estados UnidosFil: Belmaker, Amos. Tel Aviv University; IsraelFil: Ferretti, Valentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Forsman, Anna M.. University Of Central Florida; Estados UnidosFil: Gaul, Jennifer R.. International High School at La Guardia Community College; Estados UnidosFil: Llambias, Paulo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Orzechowski, Sophia C.. Harvard University; Estados UnidosFil: Shipley, Ryan. Max Planck Institute For Animal Behavior; AlemaniaFil: Wilson, Maya. Virginia Polytechnic Institute. Department Of Geological Sciences; Estados UnidosFil: Yoon, Hyun Seok. University of Tennessee; Estados Unido

High Migratory Survival and Highly Variable Migratory Behavior in Black-Tailed Godwits

Few studies have been able to directly measure the seasonal survival rates of migratory species or determine how variable the timing of migration is within individuals and across populations over multiple years. As such, it remains unclear how likely migration is to affect the population dynamics of migratory species and how capable migrants may be of responding to changing environmental conditions within their lifetimes. To address these questions, we used three types of tracking devices to track individual black-tailed godwits from the nominate subspecies (Limosa limosa limosa) throughout their annual cycles for up to 5 consecutive years. We found that godwits exhibit considerable inter- and intra-individual variation in their migratory behavior across years. We also found that godwits had generally high survival rates during migration, although survival was reduced during northward flights across the Sahara Desert. These patterns differ from those observed in most other migratory species, suggesting that migration may only be truly dangerous when crossing geographic barriers that lack emergency stopover sites and that the levels of phenotypic flexibility exhibited by some populations may enable them to rapidly respond to changing environmental conditions

In Vitro Evaluation of a Soluble Leishmania Promastigote Surface Antigen as a Potential Vaccine Candidate against Human Leishmaniasis

International audiencePSA (Promastigote Surface Antigen) belongs to a family of membrane-bound and secreted proteins present in severalLeishmania (L.) species. PSA is recognized by human Th1 cells and provides a high degree of protection in vaccinated mice.We evaluated humoral and cellular immune responses induced by a L. amazonensis PSA protein (LaPSA-38S) produced in aL. tarentolae expression system. This was done in individuals cured of cutaneous leishmaniasis due to L. major (CCLm) or L.braziliensis (CCLb) or visceral leishmaniasis due to L. donovani (CVLd) and in healthy individuals. Healthy individuals weresubdivided into immune (HHR-Lm and HHR-Li: Healthy High Responders living in an endemic area for L. major or L. infantuminfection) or non immune/naive individuals (HLR: Healthy Low Responders), depending on whether they produce high orlow levels of IFN-c in response to Leishmania soluble antigen. Low levels of total IgG antibodies to LaPSA-38S were detectedin sera from the studied groups. Interestingly, LaPSA-38S induced specific and significant levels of IFN-c, granzyme B and IL-10 in CCLm, HHR-Lm and HHR-Li groups, with HHR-Li group producing TNF-a in more. No significant cytokine response wasobserved in individuals immune to L. braziliensis or L. donovani infection. Phenotypic analysis showed a significant increasein CD4+ T cells producing IFN-c after LaPSA-38S stimulation, in CCLm. A high positive correlation was observed between thepercentage of IFN-c-producing CD4+ T cells and the released IFN-c. We showed that the LaPSA-38S protein was able toinduce a mixed Th1 and Th2/Treg cytokine response in individuals with immunity to L. major or L. infantum infectionindicating that it may be exploited as a vaccine candidate. We also showed, to our knowledge for the first time, the capacityof Leishmania PSA protein to induce granzyme B production in humans with immunity to L. major and L. infantum infectio

Molecular mechanisms underlying avian metabolic variation: a genomic approach

Physiological adaptive acclimatization allows an organism to balance the competing demands of its life cycle and environment. This thesis seeks to further our understanding of the processes underlying physiological acclimation by characterizing two molecular mechanisms that enable organisms to mount physiological responses to changing environmental conditions. Comprised of two investigations, it focuses on the molecular mechanisms underlying variation in avian aerobic performance. In the first, I explore regulatory changes that act on relatively short time periods, enabling organisms to respond to rapid environmental changes within an individual’s lifetime. I show that thermogenic flexibility manifested from simultaneous changes in the expression of genes within hierarchical regulatory networks in response to temperature in the Dark-eyed Junco (Junco hyemalis). This transcriptomic variation resulted in rapid physiological modifications within individuals. In the second, I instead characterize coding mutations that occur on the timescale of generations. I show that differences in the mitochondrial sequences of the genes encoding the machinery of cellular metabolism could result in canalized differences in whole-organism aerobic performance among Tachycineta swallow species. Sites of positive selection were concentrated in species with ‘slow’ life histories that may be associated with low metabolic rates. Together these investigations provide a concise survey of the molecular tools birds are equipped with to metabolically respond and adapt to environmental variation

Data from: Ecological mismatches are moderated by local conditions in two populations of a long-distance migratory bird

Ecological mismatches between reproductive events and seasonal resource peaks are frequently proposed to be a key driver of population dynamics resulting from global climate change. Many local populations are experiencing reduced reproductive success as a consequence of mismatches, but few mismatches have led to species-level population declines. To better understand this apparent paradox, we investigated the breeding phenology and chick survival of two disjunct populations of Hudsonian godwits Limosa haemastica breeding at Churchill, Manitoba and Beluga River, Alaska. Only one population experienced a mismatch: godwits bred nearly one week after the onset of the invertebrate peak at Churchill because of asynchronous climatic change occurring throughout their annual cycle. However, chicks were not uniformly affected by the mismatch — growth rates and survival of young chicks were not correlated with invertebrate abundance, but older chicks tended to suffer lower survival rates on days of low invertebrate abundance. Ecological mismatches thus resulted in a complex array of consequences, but nonetheless contributed to reductions in chick survival. In contrast, godwits at Beluga River hatched their chicks just before the invertebrate peak, such that the period of highest energetic need coincided with the period of highest invertebrate abundance. As a result, growth rates and survival of godwit chicks were unaffected by invertebrate abundance. Godwits at Beluga River were able to properly time their reproduction because of predictable rates of climatic change and strong selection imposed by high predation on late-hatched chicks. Taken together, our results suggest that population-specific, local-scale selection pressures play a critical role in determining the degree and severity of ecological mismatches. The potential for global climate change to induce species-level population declines may therefore be mediated by the spatial variation in the selection pressures acting across a species’ range

Churchill Daily Insect Data 2009-2011

These are the daily measurements of invertebrate biomass (mg) along our two pitfall trap transects in Churchill, Manitoba 2009-2011. Each transect was comprised of 5 pitfall traps

Beluga River Daily Insects 2009-2012

These are the daily measurements of invertebrate biomass (mg) along our two pitfall trap transects in Beluga River, Alaska 2009-2011. Each transect was comprised of 5 pitfall traps

Nest Data Churchill and Beluga 2009-2012

This file can be used in Program Mark to determine the nest survival rates of Hudsonian Godwits, Limosa haemastica, breeding in Beluga River, Alaska and Churchill, Manitoba from 2009-2011. The file includes the nest ID number, the first date on which each nest was found, the date on which it was last known to be alive, and the date on which its fate was complete (e.g., alive or dead). The final column denotes the nest's fate (0 = hatched, 1 = failed)