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1. Intraspecific variation in incubation behaviours along a latitudinal gradient is driven by nest microclimate and selection on neonate quality

   https://doi.org/10.1111/1365-2435.13772  

   Lundblad, Carl G. ; Conway, Courtney J. ; Sandercock, ed., Brett ( March 2021 , Functional Ecology)

   The strategies by which animals allocate reproductive effort across their lifetimes vary, and the causes of variation in those strategies are actively debated. In birds, most research has focused heavily on variation in clutch size and fecundity, but incubation behaviour and other functionally related traits have received less attention. Variation in incubation period duration is notable because time‐dependent sources of clutch mortality should impose strong directional selection to minimize the incubation period. However, life‐history theory predicts multiple mechanisms by which inter‐ and intraspecific variation in incubation behaviours may be adaptive.

   We conducted one of the first studies of intraspecific latitudinal variation in avian incubation behaviours across a large portion of a single species’ range. We placed motion‐activated nest cameras inside burrowing owl nests at five study sites to quantify variation in daily nest attentiveness, cumulative nest attendance and incubation period duration. We tested predictions of two alterative hypotheses that have been proposed to explain variation in incubation periods: theparental risk tolerance hypothesisand theneonate quality hypothesis.

   Daily nest attentiveness, cumulative nest attendance and incubation period duration in burrowing owls were all positively correlated with latitude. Burrowing owls reduced their daily nest attentiveness at low latitudes and on days when the average nest temperature was within the range that is optimal for embryo development. Further, longer incubation periods were most strongly associated with greater cumulative nest attendance instead of reduced daily nest attentiveness.

   These results support predictions of theneonate quality hypothesis:longer incubation periods result from stronger selection on neonate quality rather than selection to reduce reproductive effort in response to low extrinsic mortality risk. However, some owls facultatively reduced their daily nest attentiveness, and this result supports the general hypothesis that incubation decisions reflect a trade‐off between reproduction and self‐maintenance, and that the optimal solution to that trade‐off varies systematically in response to latitudinal gradients in adult mortality.

   A freePlain Language Summarycan be found within the Supporting Information of this article.

    

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2. Longitudinal dynamics and behavioural correlates of telomeres in male wire‐tailed manakins

   https://doi.org/10.1111/1365-2435.13715  

   Vernasco, Ben J. ; Dakin, Roslyn ; Majer, Ariana D. ; Haussmann, Mark F. ; Brandt Ryder, T. ; Moore, Ignacio T. ; Angelier, ed., Frédéric ( December 2020 , Functional Ecology)

   Building on the predictions of state‐dependent life‐history theory, telomeres are hypothesized to either correlate with or function as an adaptive, proximate mediator of an individual's behaviour and life‐history strategy. To further understand the relationship between telomeres, behaviour and life‐history strategies, we measured male behaviour, telomere lengths and telomere dynamics in a free‐living population of known‐age, male wire‐tailed manakinsPipra filicauda.

   Male wire‐tailed manakins perform coordinated displays with other males at leks and these displays form the basis of long‐term coalition partnerships. Males exhibit consistent individual differences in the number of social partners within their social network and the frequency of social interactions. Male sociality is also positively correlated with both social rise and reproductive success.

   We measured male behaviour using a telemetry‐based, proximity datalogging system and blood telomere lengths were quantified using qPCR. We examined the relationships between telomere length, telomere dynamics, social status, and male behaviour. We also quantified the repeatability of telomere lengths, examined age‐related changes in telomere length, and tested for instances of telomere elongation that exceed residual error in telomere length.

   Telomere length was found to be highly repeatable. More social males exhibited shorter telomeres and higher rates of telomere attrition. Telomeres did not significantly vary with age within or between individuals in either of the male social classes. Two out of 25 individuals exhibited patterns telomere elongation that exceeded residual error in telomere measurements.

   Here we show that telomeres consistently vary between male wire‐tailed manakins and these differences are related to variation in male social behaviour. In this relatively long‐lived species, telomeres appear to be flexible traits that can increase or decrease in length. Overall, this study provides observational support for the hypothesis that telomeres act as a molecular marker that relates to behaviour in a state‐dependent manner. We also provide insight into the molecular consequences of individual variation in male social behaviour.

   A freePlain Language Summarycan be found within the Supporting Information of this article.

    

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3. Climate teleconnections synchronize Picea glauca masting and fire disturbance: Evidence for a fire‐related form of environmental prediction

   https://doi.org/10.1111/1365-2745.13308  

   Ascoli, Davide ; Hacket‐Pain, Andrew ; LaMontagne, Jalene M. ; Cardil, Adrián ; Conedera, Marco ; Maringer, Janet ; Motta, Renzo ; Pearse, Ian S. ; Vacchiano, Giorgio ; Bellingham, ed., Peter ( November 2019 , Journal of Ecology)

   Synchronous pulses of seed masting and natural disturbance have positive feedbacks on the reproduction of masting species in disturbance‐prone ecosystems. We test the hypotheses that disturbances and proximate causes of masting are correlated, and that their large‐scale synchrony is driven by similar climate teleconnection patterns at both inter‐annual and decadal time scales.

   Hypotheses were tested on white spruce (Picea glauca), a masting species which surprisingly persists in fire‐prone boreal forests while lacking clear fire adaptations. We built masting, drought and fire indices at regional (Alaska, Yukon, Alberta, Quebec) and sub‐continental scales (western North America) spanning the second half of the 20th century. Superposed Epoch Analysis tested the temporal associations between masting events, drought and burnt area at the regional scale. At the sub‐continental scale, Superposed Epoch Analysis tested whether El Niño‐Southern Oscillation (ENSO) and its coupled effects with the Atlantic Multidecadal Oscillation (AMO) in the positive phase (AMO+/ENSO+) synchronize drought, burnt area and masting. We additionally tested the consistency of our synchronization hypotheses on a decadal temporal scale to verify whether long‐term oscillations in AMO+/ENSO+ are coherent to decadal variation in drought, burnt area and masting.

   Analyses demonstrated synchronicity between drought, fire and masting. In all regions the year before a mast event was drier and more fire‐prone than usual. During AMO+/ENSO+ events sub‐continental indices of drought and burnt area experienced significant departures from mean values. The same was observed for large‐scale masting in the subsequent year, confirming 1‐year lag between fire and masting. Sub‐continental indices of burnt area and masting showed in‐phase decadal fluctuations led by the AMO+/ENSO+. Results support the ‘Environmental prediction hypothesis’ for mast seeding.

   Synthesis. We provide evidence of large‐scale synchronicity between seed masting inPicea glaucaand fire regimes in boreal forests of western North America at both inter‐annual and decadal time scales. We conclude that seed production in white spruce predicts changes in disturbance regimes by sharing the same large‐scale climate drivers with drought and fire. This gives new insides in a mechanism providing a fire‐sensitive species with higher than expected adaptability to changes in climate.

    

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4. Survival is negatively related to basal metabolic rate in tropical Andean birds

   https://doi.org/10.1111/1365-2435.13375  

   Scholer, Micah N. ; Arcese, Peter ; Puterman, Martin L. ; Londoño, Gustavo A. ; Jankowski, Jill E. ; Portugal, ed., Steven ( June 2019 , Functional Ecology)

   Life‐history theory postulates that physiological traits, such as energy metabolism, can be understood in terms of allocation trade‐offs between self‐maintenance and reproduction over an organism's life span, and data show that metabolic intensity and survival vary inversely with latitude, with tropical birds exhibiting a “slow” pace of life relative to temperature species. However, tropical regions harbour strong environmental gradients of their own, and it remains to be shown whether similar life‐history trade‐offs between metabolism and longevity are reflected among tropical birds of the same latitude.

   We estimated apparent annual survival in 37 species of tropical passerine birds along an elevational gradient (400–3,000 m) in Peru to test whether variation in survival was influenced by basal metabolic rate (BMR; estimated at the same sites), elevation or both factors. We used path analysis to test our prediction that survival would decline as BMR increased, while accounting for the potential direct effects of elevation on survival due to differences in predation pressure or environmental conditions as well as potential indirect effects of elevation on BMR via temperature and the costs of thermoregulation.

   Higher BMR in tropical passerine birds predicted lower apparent survival, regardless of the elevation at which species occurred. In addition, elevation had a direct negative effect on apparent survival, perhaps due to harsher abiotic conditions, low site fidelity or both at high elevations.

   We provide evidence of a link between metabolic rate and longevity previously undescribed in populations of free‐living birds. Our results illustrate that tropical montane species may be characterized by a unique suite of traits in their pace of life, in which BMR does not differ from lowland birds, but survival does.

   Aplain language summaryis available for this article.

    

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5. Effects of large mammal exclusion on seedling communities depend on plant species traits and landscape protection in human‐modified Costa Rican forests

   https://doi.org/10.1111/1365-2664.14531  

   Huanca‐Nuñez, Nohemi ; Chazdon, Robin L. ; Russo, Sabrina E. ( November 2023 , Journal of Applied Ecology)

   Large terrestrial herbivorous mammals (LTH‐mammals) influence plant community structure by affecting seedling establishment in mature tropical forests. Many of these LTH‐mammals frequent secondary forests, but their effects on seedling establishment in them are understudied, hindering our understanding of how LTH‐mammals influence forest regeneration in human‐modified landscapes.

   We tested the hypothesis that the strength of LTH‐mammals' effects on seedling establishment depends on landscape protection, forest successional stage and plant species' traits using a manipulative field experiment in six 1‐ha sites with varying successional age and landscape protection. In each site, we established 40 seedling plot‐pairs, with one plot excluding LTH‐mammals and one not, and monitored seedlings of 116 woody species for 26 months.

   We found significant effects of LTH‐mammal exclusion on seedling survival contingent upon the protection of forests at the landscape level and forest stage. After 26 months, survival differences between LTH‐mammal exclusion and non‐exclusion treatments were greater in protected than unprotected landscapes. Additionally, plant species' traits were related to the LTH‐mammals' differential effects, as LTH‐mammals reduced the survival of seedlings of larger‐seeded species the most. Overall, LTH‐mammals' effects translated into significant shifts in community composition as seedling communities inside and outside the exclosures diverged. Moreover, lower density and higher species diversity were found as early as 12 and 18 months outside than inside exclosures.

   Synthesis and applications.Insight into the interactions between LTH‐mammals and seedling communities in forest regeneration can be instrumental in planning effective restoration efforts. We highlight the importance of landscape protection in seedling survival and the role of LTH‐mammals in promoting seedling diversity in mature forests but also in secondary successional forests. The findings suggest that conservation efforts and possibly trophic rewilding can be important approaches for preserving diversity and influencing the trajectory of secondary tropical forest succession. However, we also caution that an overabundance of LTH‐mammals may adversely impact the pace of forest succession due to their preference for large‐seeded species. Therefore, a comprehensive wildlife management plan is indispensable. Additionally, longer term studies on LTH‐mammals are necessary to understand the effects of temporal fluctuations that are undetected in short‐term studies.

    

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