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1. Differences in perceived predation risk associated with variation in relative size of extra‐pair and within‐pair offspring

   https://doi.org/10.1111/jeb.13564  

   Hallinger, Kelly K. ; Vitousek, Maren N. ; Winkler, David W. ( November 2019 , Journal of Evolutionary Biology)

   Extra‐pair paternity (EPP) is a widespread phenomenon in birds. Researchers have long hypothesized that EPP must confer a fitness advantage to extra‐pair offspring (EPO), but empirical support for this hypothesis is definitively mixed. This could be because genetic benefits of EPP only exist in a subset of environmental contexts to which a population is exposed. From 2013 to 2015, we manipulated perceived predator density in a population of tree swallows (Tachycineta bicolor) breeding in New York to see whether fitness outcomes of extra‐pair and within‐pair offspring (WPO) varied with predation risk. In nests that had been exposed to predators, EPO were larger, longer‐winged and heavier than WPO. In nonpredator nests, WPO tended to be larger, longer‐winged and heavier than EPO, though the effect was nonsignificant. We found no differences in age, morphology or stress physiology between extra‐pair and within‐pair sires from the same nest, suggesting that additive genetic benefits cannot fully explain the differences in nestling size that we observed. The lack of an effect of predator exposure on survival or glucocorticoid stress physiology of EPO and WPO further suggests that observed size differences do not reflect more general variation in intrinsic genetic quality. Instead, we suggest that size differences may have arisen through differential investment into EPO and WPO by females, perhaps because EPO and WPO represent different reproductive strategies, with each type of nestling conferring a fitness advantage in specific ecological contexts.

    

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2. Behavioral estimates of mating success corroborate genetic evidence for pre-copulatory selection

   https://doi.org/10.1093/beheco/arad099  

   Bhave, Rachana S. ; Seears, Heidi A. ; Reedy, Aaron M. ; Wittman, Tyler N. ; Robinson, Christopher D. ; Cox, Robert M. ; DuVal, ed., Emily ( December 2023 , Behavioral Ecology)

   In promiscuous species, fitness estimates obtained from genetic parentage may often reflect both pre- and post-copulatory components of sexual selection. Directly observing copulations can help isolate the role of pre-copulatory selection, but such behavioral data are difficult to obtain in the wild and may also overlook post-copulatory factors that alter the relationship between mating success and reproductive success. To overcome these limitations, we combined genetic parentage analysis with behavioral estimates of size-specific mating in a wild population of brown anole lizards (Anolis sagrei). Males of this species are twice as large as females and multiple mating among females is common, suggesting the scope for both pre- and post-copulatory processes to shape sexual selection on male body size. Our genetic estimates of reproductive success revealed strong positive directional selection for male size, which was also strongly associated with the number of mates inferred from parentage. In contrast, a male’s size was not associated with the fecundity of his mates or his competitive fertilization success. By simultaneously tracking copulations in the wild via the transfer of colored powder to females by males from different size quartiles, we independently confirmed that large males were more likely to mate than small males. We conclude that body size is primarily under pre-copulatory sexual selection in brown anoles, and that post-copulatory processes do not substantially alter the strength of this selection. Our study also illustrates the utility of combining both behavioral and genetic methods to estimate mating success to disentangle pre- and post-copulatory processes in promiscuous species.

    

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3. The influence of subcolony-scale nesting habitat on the reproductive success of Adélie penguins

   https://doi.org/10.1038/s41598-021-94861-7  

   Schmidt, Annie E. ; Ballard, Grant ; Lescroël, Amélie ; Dugger, Katie M. ; Jongsomjit, Dennis ; Elrod, Megan L. ; Ainley, David G. ( December 2021 , Scientific Reports)

   null (Ed.)

   Abstract Group-size variation is common in colonially breeding species, including seabirds, whose breeding colonies can vary in size by several orders of magnitude. Seabirds are some of the most threatened marine taxa and understanding the drivers of colony size variation is more important than ever. Reproductive success is an important demographic parameter that can impact colony size, and it varies in association with a number of factors, including nesting habitat quality. Within colonies, seabirds often aggregate into distinct groups or subcolonies that may vary in quality. We used data from two colonies of Adélie penguins 73 km apart on Ross Island, Antarctica, one large and one small to investigate (1) How subcolony habitat characteristics influence reproductive success and (2) How these relationships differ at a small (Cape Royds) and large (Cape Crozier) colony with different terrain characteristics. Subcolonies were characterized using terrain attributes (elevation, slope aspect, slope steepness, wind shelter, flow accumulation), as well group characteristics (area/size, perimeter-to-area ratio, and proximity to nest predators). Reproductive success was higher and less variable at the larger colony while subcolony characteristics explained more of the variance in reproductive success at the small colony. The most important variable influencing subcolony quality at both colonies was perimeter-to-area ratio, likely reflecting the importance of nest predation by south polar skuas along subcolony edges. The small colony contained a higher proportion of edge nests thus higher potential impact from skua nest predation. Stochastic environmental events may facilitate smaller colonies becoming “trapped” by nest predation: a rapid decline in the number of breeding individuals may increase the proportion of edge nests, leading to higher relative nest predation and hindering population recovery. Several terrain covariates were retained in the final models but which variables, the shapes of the relationships, and importance varied between colonies. 

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4. Effects of experimental light at night on extra‐pair paternity in a songbird

   https://doi.org/10.1002/jez.2193  

   de Jong, Maaike ; Lamers, Koosje P. ; Eugster, Mark ; Ouyang, Jenny Q. ; Da Silva, Arnaud ; Mateman, A. Christa ; van Grunsven, Roy H. A. ; Visser, Marcel E. ; Spoelstra, Kamiel ( June 2018 , Journal of Experimental Zoology Part A: Ecological and Integrative Physiology)

   Light pollution is increasing worldwide and significantly affects animal behavior. In birds, these effects include advancement of morning activity and onset of dawn song, which may affect extra‐pair paternity. Advanced dawn song of males may stimulate females to engage in extra‐pair copulations, and the earlier activity onset may affect the males’ mate guarding behavior. Earlier work showed an effect of light at night on extra‐pair behavior, but this was in an area with other anthropogenic disturbances. Here, we present a two‐year experimental study on effects of light at night on extra‐pair paternity of great tits (Parus major). Previously dark natural areas were illuminated with white, red, and green LED lamps and compared to a dark control. In 2014, the proportion of extra‐pair young in broods increased with distance to the red and white lamps (i.e., at lower light intensities), but decreased with distance to the poles in the dark control. In 2013, we found no effects on the proportion of extra‐pair young. The total number of offspring sired by a male was unaffected by artificial light at night in both years, suggesting that potential changes in female fidelity in pairs breeding close to white and red light did not translate into fitness benefits for the males of these pairs. Artificial light at night might disrupt the natural patterns of extra‐pair paternity, possibly negates potential benefits of extra‐pair copulations and thus could alter sexual selection processes in wild birds.

    

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5. Paternity in wild ring‐tailed lemurs ( Lemur catta ): Implications for male mating strategies

   https://doi.org/10.1002/ajp.22584  

   Parga, Joyce A. ; Sauther, Michelle L. ; Cuozzo, Frank P. ; Youssouf Jacky, Ibrahim Antho ; Lawler, Richard R. ; Sussman, Robert W. ; Gould, Lisa ; Pastorini, Jennifer ( July 2016 , American Journal of Primatology)

   In group‐living species with male dominance hierarchies where receptive periods of females do not overlap, high male reproductive skew would be predicted. However, the existence of female multiple mating and alternative male mating strategies can call into question single‐male monopolization of paternity in groups. Ring‐tailed lemurs (Lemur catta) are seasonally breeding primates that live in multi‐male, multi‐female groups. Although established groups show male dominance hierarchies, male dominance relationships can break down during mating periods. In addition, females are the dominant sex and mate with multiple males during estrus, including group residents, and extra‐group males—posing the question of whether there is high or low male paternity skew in groups. In this study, we analyzed paternity in a population of wildL. cattafrom the Bezà Mahafaly Special Reserve in southwestern Madagascar. Paternity was determined with 80–95% confidence for 39 offspring born to nine different groups. We calculated male reproductive skew indices for six groups, and our results showed a range of values corresponding to both high and low reproductive skew. Between 21% and 33% of offspring (3 of 14 or three of nine, counting paternity assignments at the 80% or 95% confidence levels, respectively) were sired by extra‐troop males. Males siring offspring within the same group during the same year appear to be unrelated. Our study provides evidence of varying male reproductive skew in differentL. cattagroups. A single male may monopolize paternity across one or more years, while in other groups, >1 male can sire offspring within the same group, even within a single year. Extra‐group mating is a viable strategy that can result in extra‐group paternity forL. cattamales.

    

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