Temporal variation in size-assortative mating and male mate choice in a spider with amphisexual care

Seasonal variation in cuckoldry rates in the socially monogamous cichlid fish Variabilichromis moorii

Mating patterns in animal populations can respond to environmental conditions and consequently vary across time. To examine this variation in nature, studies must include temporal replicates from the same population. Here, we report temporal variation in genetic parentage in the socially monogamous cichlid Variabilichromis moorii from Lake Tanganyika, using samples of broods and their brood-tending parents that were collected across five field trips from the same study population. The sampled broods were either spawned during the dry season (three field trips) or during the rainy season (two trips). In all seasons, we detected substantial rates of extra-pair paternity, which were ascribed to cuckoldry by bachelor males. Paternity shares of brood-tending males were consistently higher, and the numbers of sires per brood were consistently lower, in broods that were spawned in the dry seasons compared to broods from the rainy seasons. In contrast, the strength of size-assortative pairing in our V. moorii population did not vary temporally. Seasonal fluctuations in environmental conditions, such as water turbidity, are proposed as a mechanism behind variable cuckolder pressure. Our data demonstrate the utility of long-term monitoring to improve our understanding of animal mating patterns.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10750-022-05042-0.

Araneophagy as an alternative foraging tactic to kleptoparasitism in two Argyrodinae (Araneae: Theridiidae) species

Kleptoparasitism is assumed to be the main foraging strategy in some animal groups, such as the spiders of the subfamily Argyrodinae (Theridiidae). However, some species may also feed on silk threads, egg sacs, or even their hosts. The conditions determining these alternative foraging tactics remain unknown for most species. We performed field observations, stable isotope analysis and laboratory experiments to investigate kleptoparasitism and araneophagy of Argyrodes elevatus and Faiditus caudatus in webs of Manogea porracea (Araneidae). We evaluated the following hypotheses: (1) both species exhibit higher trophic positions than their hosts and closest to an araneophagic sympatric species; (2) host web selection is influenced by the presence of alternative resources (adult male and female, and egg sacs); and (3) they preferentially consume egg sacs instead of stored prey items. Both argyrodines showed higher trophic positions than their female hosts and closest to an araneophagic spider species. The invaders were found mainly on host webs with one adult and egg sacs and with egg sacs only. Finally, A. elevatus preferred to feed on prey captured by the host spider instead of egg sacs. We discussed the factors that can potentially determine the choices between foraging exclusively as kleptoparasites and consuming the hosts.

Assortative mating in space and time: patterns and biases

Despite the important roles of assortative mating for understanding evolutionary processes, our knowledge on the variation in assortative mating across populations and breeding periods has been overshadowed by the greater attention given to general patterns. Obtaining data on mating pairs are difficult for most species; therefore, researchers often group data from different populations or breeding periods, which can increase positive biases in detecting and estimating assortative mating. We used a meta-analytic approach to investigate the biases caused by spatially or temporally pooling data and the assortative mating consistency across populations and breeding periods. We describe assortative mating patterns across and within animal taxa. We performed a systematic review to search studies reporting measures of size-assortative mating (SAM). Grouping data from multiple populations and seasons incurred positive biases. Overall, assortative mating moderately exhibited low repeatability in space and time, but it was inconsistent for most taxa. After excluding pooled measures, the average estimate for assortative mating was moderate and positive. Thus, our findings demonstrate that pooling data can produce misleading results. We also highlight the importance of further investigation of hypotheses that explain spatial and temporal variation in assortative mating, after its detection. Our study reinforces the significance of investigating mating patterns at various spatial and temporal scales before drawing broad conclusions.