Intersexual Resource Competition and the Evolution of Sex-Biased Dispersal

Abstract

Resource competition is a major driver of dispersal: an emigrating individual leaves more resources to its kin. Existing models of sex-biased dispersal rarely consider intersexual competition for resources. Instead, male reproductive success is often solely assumed to depend on female availability, implying a tacit assumption that male presence never depletes resources, such as food, that are of interest to female kin. In reality, both male and female offspring typically consume resources on their natal site before departing to consume resources elsewhere, and sexually dimorphic body sizes imply that the resource needs can differ. The goal of our study is to investigate how intersexual competition for resources can affect the evolution of sex-specific dispersal, via competition between kin of the same sex or different sexes and the subsequent success elsewhere. Our individual-based simulation model allows not only the dispersal probability but also its timing to evolve. We consider dispersal timing because later dispersal yields a longer period of kin competition than dispersal that occurs soon after independence. We also highlight the role of sex-specific income/capital breeding strategies, which is understudied in both empirical and theoretical literature of sex-specific dispersal. We show that sex biases in dispersal probability and timing are sensitive to the presence of intersexual competition, sexual differences in capital vs. income breeding strategies, and sexual dimorphism in the quantity of resources consumed. Males may evolve to disperse earlier if they also consume more food, as a result of selection to reduce intersexual kin competition. Alternatively, males may evolve to disperse less as well as later than females, if male fitness depends more on resource accumulation (e.g., building a large body to succeed in mating competition under polygyny) whereas female fitness depends more on reliable income (e.g., in species that require extended periods of maternal foraging), even if both sexes are equally competitive in consuming resources. Although the more dispersive sex is often the earlier departing sex, we also find cases where the only clear dimorphism is found in dispersal timing. We thus encourage more studies on the timing aspect of sex-biased dispersal.

Genetic analysis indicates spatial-dependent patterns of sex-biased dispersal in Eurasian lynx in Finland

“…In contrast, in the western part of our study area, the process of lynx recolonization was still ongoing in the beginning of the sampling period, and thus probably did not represent a saturated population with a stable social organization until around 2010 (Holmala unpublished ). These different colonization stages may explain the observed spatial variation in sex-specific autocorrelation, which was mainly due to spatial variation in the organization of the females caused by differences in population density and resource availability [ 74 , 75 ]. Eurasian lynx shows large variation in dispersal distances, with both short and long-distance dispersal for both sexes [ 21 – 23 , 25 , 76 ].…”

Spatial connectedness imposes local‐ and metapopulation‐level selection on life history through feedbacks on demography

“…The evolution of dispersal timing has been theoretically addressed in response to either dispersal at adulthood (breeding dispersal) or at birth (natal dispersal) (Johst & Brandl, ; Hirota, ; Lakovic et al, , ), and only recent studies have started addressing the issue at a more detailed time scale (Li & Kokko, ). Here, we found evolved breeding dispersal to be delayed in the least connected metapopulations.…”

Increased population density depresses activity but does not influence emigration in the snailPomatias elegans

“…Broadly, sex-dependent dispersal is predicted to arise when there are sex-differences in spatio-temporal fitness variation due to e.g. sex differences in resource use and/or in local mate competition (Hovestadt, Mitesser & Poethke, 2014; Trochet et al , 2016; Li & Kokko, 2019). Our results, in light of dispersal theory, imply that male and female P. elegans use resources similarly and that they do not present polygyny or any mating system leading to predictable sex differences in spatio-temporal fitness variation.…”

“…We should additionally note that our experimental setup (one measure of dispersal, after 4 days, and groups that were sex-balanced on average) may not have allowed us to detect finer sex differences in dispersal, i.e. in timing (Li & Kokko, 2019), or conditional strategies dependent on locally experienced sex-ratio (Hovestadt et al , 2014).…”