Multiple paternity is a shared reproductive strategy in the live-bearing surfperches (Embiotocidae) that may be associated with female fitness

Does the potential strength of sexual selection differ between mating systems with and without defensive behaviours? A meta-analysis

The Darwin-Bateman paradigm predicts that females enhance their fitness by being choosy and mating with high-quality males, while males should compete to mate with as many females as possible. In many species, males enhance their fitness by defending females and/or resources used by females. That is, males directly defend access to mating opportunities. However, paternity analyses have repeatedly shown that females in most species mate polyandrously, which contradicts traditional expectations that male defensive behaviours lead to monandry. Here, in an extensive meta-analysis, encompassing 109 species and 1026 effect sizes from across the animal kingdom, we tested if the occurrence of defensive behaviours modulates sexual selection on females and males. If so, we can illuminate the extent to which males really succeed in defending access to mating and fertilisation opportunities. We used four different indices of the opportunity for sexual selection that comprise pre-mating and/or post-mating episodes of selection. We found, for both sexes, that the occurrence of defensive behaviours does not modulate the potential strength of sexual selection. This implies that male defensive behaviours do not predict the true intensity of sexual selection. While the most extreme levels of sexual selection on males are in species with male defensive behaviours, which indicates that males do sometimes succeed in restricting females' re-mating ability (e.g. elephant seals, Mirounga leonina), estimates of the opportunity for sexual selection vary greatly across species, regardless of whether or not defensive behaviours occur. Indeed, widespread polyandry shows that females are usually not restricted by male defensive behaviours. In addition, our results indicate that post-mating episodes of selection, such as cryptic female choice and sperm competition, might be important factors modulating the opportunity for sexual selection. We discuss: (i) why male defensive behaviours fail to lower the opportunity for sexual selection among females or fail to elevate it for males; (ii) how post-mating events might influence sexual selection; and (iii) the role of females as active participants in sexual selection. We also highlight that inadequate data reporting in the literature prevented us from extracting effect sizes from many studies that had presumably collected the relevant data.

In the surf zone: Reproductive strategy of the calico surfperch (Amphistichus koelzi) in a comparative context

We examined the reproductive life history of calico surfperch (Amphistichus koelzi), including mating season, pregnancy, gestation and multiple paternity utilizing restriction site-associated DNA sequencing. Furthermore, we compared the mating season of calico with barred (Amphistichus argenteus), walleye (Hyperprosopon argenteum) and silver (Hyperprosopon ellipticum) surfperches to determine if the timing of reproduction is divergent within and between the genera. In calico surfperch, the mating season occurs from October to November, and females gestate from December to May. All broods exhibit multiple paternity with a range of four to seven sires per brood. The mating season of calico overlaps completely with barred surfperch; however, barred surfperches have a protracted mating season which extends until the beginning of December, which may be due to differences in reproductive strategy such as size at first reproduction. In the genus, the Hyperprosopon mating season begins earlier than Amphistichus, with divergence in the onset of mating between Hyperprosopon congeners of approximately 1 month.

Where are all the moms? External fertilization predicts the rise of male parental care in bony fishes

Parental care shows remarkable variation across the animal kingdom, but while maternal and biparental care are common in terrestrial organisms, male-only care dominates in aquatic species that provide care. Using the most complete phylogenetic tree of bony fishes to date, we test whether the opportunity for external fertilization in aquatic environments can explain the more frequent evolution of male care in this group. We show that paternal care has evolved at least 30 times independently in fish and is found exclusively in externally fertilizing species. Male care is positively associated with pair spawning, suggesting that confidence in paternity is an important determinant of the evolution of care. Crucially, while female care is constrained by other forms of reproductive investment, male care occurs more frequently when females invest heavily in gamete production. Our results suggest that moving control of fertilization outside of the female reproductive tract raises male confidence in parentage and increases the potential for paternal care, highlighting that in an aquatic environment in which fertilization is external, paternal care is an effective reproductive strategy.

Mating System, Reproductive Success, and Sexual Selection in Bluntnose Klipfishes (Clinus cottoides)

A critical part of the sexual selection process in animals is the genetic mating system. Quantifying mating systems, especially in species with cryptic life histories can be challenging. One approach is to use genotypic markers and accurate parentage analysis, along with methods to account for bias when sampling natural populations, to calculate sexual selection metrics derived from Bateman's principles. In this study, 3 microsatellites were used to genotype 48 adults (23 female and 25 male) and 342 offspring from known mothers of live-bearing bluntnose klipfish. Parentage analysis was performed to interpret mating and reproductive success for both sexes. Metrics quantified were the opportunity for selection (I), the opportunity for sexual selection (Is), absolute (βss), and standardized (β'ss) Bateman gradients and the maximum intensity of precopulatory sexual selection (s'max). Multiple mating by both sexes were revealed by parentage analysis. However, females did not show significant Bateman gradients or a significant maximum intensity of precopulatory sexual selection (s'max), whereas male sexual selection metrics were all significantly greater than 0. These results suggest a polygynandrous mating system for this species. There is an opportunity for sexual selection to act on males but not females in this population, which is evolutionary tied to anisogamy, parental investment, and sex roles.

Does polyandry really pay off? The effects of multiple mating and number of fathers on morphological traits and survival in clutches of nesting green turtles at Tortuguero

Despite the long debate of whether or not multiple mating benefits the offspring, studies still show contradictory results. Multiple mating takes time and energy. Thus, if females fertilize their eggs with a single mating, why to mate more than once? We investigated and inferred paternal identity and number of sires in 12 clutches (240 hatchlings) of green turtles (Chelonia mydas) nests at Tortuguero, Costa Rica. Paternal alleles were inferred through comparison of maternal and hatchling genotypes, and indicated multiple paternity in at least 11 of the clutches (92%). The inferred average number of fathers was three (ranging from 1 to 5). Moreover, regression analyses were used to investigate for correlation of inferred clutch paternity with morphological traits of hatchlings fitness (emergence success, length, weight and crawling speed), the size of the mother, and an environmental variable (incubation temperature). We suggest and propose two different comparative approaches for evaluating morphological traits and clutch paternity, in order to infer greater offspring survival. First, clutches coded by the exact number of fathers and second by the exact paternal contribution (fathers who gives greater proportion of the offspring per nest). We found significant differences (P < 0.05) in clutches coded by the exact number of fathers for all morphological traits. A general tendency of higher values in offspring sired by two to three fathers was observed for the length and weight traits. However, emergence success and crawling speed showed different trends which unable us to reach any further conclusion. The second approach analysing the paternal contribution showed no significant difference (P > 0.05) for any of the traits. We conclude that multiple paternity does not provide any extra benefit in the morphological fitness traits or the survival of the offspring, when analysed following the proposed comparative statistical methods.