Ashmole's hypothesis and the latitudinal gradient in clutch size

Lundblad, Carl G.; Conway, Courtney J.

doi:10.1111/brv.12705

Cited by 14 publications

(13 citation statements)

References 148 publications

(262 reference statements)

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“…Yet, asynchronous hatching has evolved independently in numerous avian lineages (Stoleson and Beissinger 1995), and many causal hypotheses have been proposed that assume that asynchronous hatching is adaptive and is part of an explicit life‐history strategy (Lack 1947, Magrath 1990, Stoleson and Beissinger 1995). Well‐known explanations proposed for both asynchronous hatching and the correlation between clutch size and latitude have largely focused on biotic processes such as variation in food limitation and predation risk (e.g., Lack 1947, Skutch 1949, Ashmole 1961, Ricklefs 1980, Magrath 1990, Lundblad and Conway 2021a). In contrast, less attention has been given to abiotic and thermal mechanisms that could explain these two ubiquitous patterns (but see Cody 1966, Stoleson and Beissinger 1999, Reid et al 2000, Cooper et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Nest microclimate and limits to egg viability explain avian life‐history variation across latitudinal gradients

Lundblad

Conway

2021

Ecology

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Variation in life‐history strategies is central to our understanding of population dynamics and how organisms adapt to their environments. Yet we lack consensus regarding the ecological processes that drive variation in traits related to reproduction and survival. For example, we still do not understand the cause of two widespread inter‐ and intraspecific patterns: (1) the ubiquitous positive association between avian clutch size and latitude; and (2) variation in the extent of asynchronous hatching of eggs within a single clutch. Well‐known hypotheses to explain each pattern have largely focused on biotic processes related to food availability and predation risk. However, local adaptation to maintain egg viability could explain both patterns with a single abiotic mechanism. The egg viability hypothesis was initially proposed to explain the cause of asynchronous hatching and suggests that asynchronous hatching results from early incubation onset in response to unfavorable nest microclimatic conditions, which otherwise reduce egg viability. However, allocation of resources to early incubation, prior to clutch completion, may energetically constrain clutch size and help explain the positive association between clutch size and latitude. We measured intraspecific variation in five functionally linked life‐history traits of burrowing owls at five study sites spanning a 1,400‐km latitudinal transect in western North America: clutch size, the timing of incubation onset, the degree of hatching asynchrony, the probability of hatching failure, and nestling survival. We found that most traits varied clinally with latitude, but all the traits were more strongly associated with individual nest microclimates than with latitude, and all varied with nest microclimate in the directions predicted by the egg viability hypothesis. Furthermore, incubation began earlier, hatching asynchrony increased, and clutch size declined across the breeding season. These results suggest that nest microclimate drives an important life‐history trade‐off and that thermal gradients are often sufficient to account for observed biogeographic and seasonal patterns in life‐history strategies. Furthermore, our results reveal a potentially important indirect mechanism by which reproductive success and recruitment could be affected by climate change.

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Section: Introductionmentioning

confidence: 99%

Nest microclimate and limits to egg viability explain avian life‐history variation across latitudinal gradients

Lundblad

Conway

2021

Ecology

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“…In birds, clutch size generally increases with latitude, the cause of which has been the focus of many competing classical hypotheses (i.e. Lack's rule, Ashmole's hypothesis, reviewed in Lundblad & Conway, 2021). This background led us to expect that clutch size in A. bruennichi would increase with latitude, which makes it all the more interesting that we find the opposite pattern.…”

Section: Reproductive Successmentioning

confidence: 74%

Rapid ecological and evolutionary divergence during a poleward range expansion

Sheffer

Zander

Schulze

et al. 2021

Preprint

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Anthropogenic climate change is rapidly altering ecosystems, driving range shifts, range contractions, dwindling population sizes and local extinctions in many species. Some species, however, are expanding their ranges and seem to benefit from warming temperatures. This is the case for the wasp spider, Argiope bruennichi, which has undergone a range expansion from its historic range in the Mediterranean (“core”), now reaching as far as the Baltic states and Scandinavia (“edge”). The rate of this range expansion cannot be attributed to climate change alone, and it has been hypothesized that adaptive introgression lent the genetic variation upon which selection could act, enabling the rapid range expansion. In the present study, we first quantify the degree of local adaptation and phenotypic plasticity in cold tolerance in edge relative to core populations, and secondly investigate genomic and phenotypic turnover across the proposed introgression zone. With a reciprocal transplant common garden experiment, we provide strong support for the hypothesis that edge populations are locally adapted to colder winter conditions. We also find evidence of seasonal plasticity in the core populations, while edge populations have lost this plasticity. Our genome-wide analysis, using a combination of FST outlier and genetic-environment association tests, supports the hypothesis that adaptive introgression played a role in environmental adaptation.

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“…Older and larger parents, and parents rearing broods in safe habitats can benefit from the increased reproductive potential resulting from rearing more male offspring. Yet, the adaptability of brood size may depend on life history traits, population demographics, and biogeographical distribution of species (Skutch 1949, Skutch 1967, Lundblad and Conway 2021a. For instance, tropical birds tend to have small clutches that rarely vary in number regardless of whether parental care is provided by one or two parents (Skutch 1949).…”

Section: Effect Of Treatments On Habitat Selection By Adult Females and Malesmentioning

confidence: 99%

Variation in song structure of house wrens living in urban and rural areas in a Caribbean small island developing state

et al. 2020

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The negative effects of anthropogenic noise on wildlife, particularly birds, have been widely studied but major gaps in scientific knowledge remain. The inequality of information available and studies conducted between the high-income countries of the Global North, and middle-and low-income countries of the Global South is limiting the applicability and implementation of conservation projects. I investigated the effects of noise in two different contexts: effects of noise from oil extraction in the North American grasslands on chestnut-collared longspurs (Calcarius ornatus) and effects of noise from urban activity in the Caribbean island of Grenada on house wrens (Troglodytes aedon). I tested whether distance from oil development, distance from infrastructure noise, brood size, and parent size and weight affected nestling sex ratio allocation in chestnut-collared longspurs. Large broods were skewed towards male nestlings, and bigger females and older social males reared more male nestlings, indicating that competitiveness and experience may be valuable traits for successful breeding and greater fitness in adults. Male nestlings were also more likely to be produced further from screwpump and silent playback treatments, suggesting that habitat farthest from anthropogenic development favours production of male nestlings. My results suggest that both biological and environmental characteristics interact to regulate sex ratio allocation in my study population. Conservation I want to thank my advisor, Nicola Koper. Nicky has let me progress and find my way through the difficulties of graduate school without judgment and helped make my experience a positive one. She believed in me as a researcher and I could not have asked more from an advisor.For their time, support, and positive attitudes, I want to thank my committee members Rachel Vallender, Margaret Docker, and Kevin Ellison. Countless people have helped me and were vital to the completion of this project. I would have no results if it wasn't for Chelsea Enslow, Erin Wieler and Arfa Khan's assistance in the lab. Thank you to all my predecessors and fellow graduate students for all the knowledge and skills you have shared with me, as well as for your friendships: Patricia Rosa,

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Ashmole's hypothesis and the latitudinal gradient in clutch size

Cited by 14 publications

References 148 publications

Nest microclimate and limits to egg viability explain avian life‐history variation across latitudinal gradients

Nest microclimate and limits to egg viability explain avian life‐history variation across latitudinal gradients

Rapid ecological and evolutionary divergence during a poleward range expansion

Variation in song structure of house wrens living in urban and rural areas in a Caribbean small island developing state

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