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In species with biparental care, conflict arises over how much each parent provides to their offspring because both parents benefit from shifting the burden of care to the other. Here, we tested alternative hypotheses for how parents will negotiate offspring care using a wild population of clownfish (Amphiprion percula). We experimentally handicapped parents by fin-clipping the female in 23 groups, the male in 23 groups, and neither parent in 23 groups and measured changes in indicators of female, male, and pair effort in response to handicapping. First, we found that handicapping resulted in a decrease in the number of eggs laid by fin-clipped females and a decrease in the amount of parental care by fin-clipped males. Second, contrary to predictions, female effort did not change in response to the male being handicapped, or vice versa. Finally, the number of embryos that matured to hatching, an indicator of pair effort, was not influenced by the manipulation, suggesting that although the handicap was effective, clownfish do not face the predicted "cost to conflict" when one parent is handicapped. Together, these results test the generality of theoretical predictions and uncover novel questions about whether and how negotiations operate in systems where interests are aligned. [ABSTRACT FROM AUTHOR]

Many animals exhibit size-assortative mating, and matching theory predicts this occurs because both males and females prefer bigger mates. Monogamy and size-assortative pairing have been described for coral reef fishes, but the underlying behavioral mechanism has not been tested. Here, we took a long-term observational and experimental study to resolve the causes of size-based pairing in the paternal mouthbrooding coral reef cardinalfish Sphaeramia nematoptera. For 65 pairs observed over a 23-month period, there was a strong size-correlation between paired males and females. This size-assortative mating was not a consequence of pairing at a young age as re-pairing was common, with only 7% juvenile pairs still found together after 8 months. For adults that changed partners over this period, there was a strong correlation between the size of individuals and the size of their new partners. Following experimental removal of partners, both males and females quickly repaired with partners of similar or larger size. Together, these results suggest that size-assortative mating is explained by a mutual preference by both males and females for larger mates. We suggest that monogamous pairing occurs in cardinalfish because mouthbrooding restricts multiple mating by males. Size-assortative pairing follows as larger males likely prefer the more fecund larger females, and larger females prefer larger males because they can successfully brood all of their eggs. Mutual mate choice will likely explain size-assortative pairing in other fish species with paternal care. [ABSTRACT FROM AUTHOR]

The relationship between genetic diversity and species diversity provides insights into biogeography and historic patterns of evolution and is critical for developing contemporary strategies for biodiversity conservation. Although concordant large-scale clines in genetic and species diversity have been described for terrestrial organisms, whether these parameters co-vary in marine species remains largely unknown. We examined patterns of genetic diversity for 11 coral reef fish species sampled at three locations across the Pacific Ocean species diversity gradient (Australia: ∼1600 species; New Caledonia: ∼1400 species; French Polynesia: ∼800 species). Combined genetic diversity for all 11 species paralleled the decline in species diversity from West to East, with French Polynesia exhibiting lowest total haplotype and nucleotide diversities. Haplotype diversity consistently declined toward French Polynesia in all and nucleotide diversity in the majority of species. The French Polynesian population of most species also exhibited significant genetic differentiation from populations in the West Pacific. A number of factors may have contributed to the general positive correlation between genetic and species diversity, including location and time of species origin, vicariance events, reduced gene flow with increasing isolation, and decreasing habitat area from West to East. However, isolation and habitat area, resulting in reduced population size, are likely to be the most influential. [ABSTRACT FROM AUTHOR]