Four polymorphic microsatellite loci were used to assess biological parentage of 453 offspring from 15 pregnant males from a natural population of the Western Australian seahorse Hippocampus angustus. Microsatellite genotypes in the progeny arrays were consistent with a monogamous mating system in which both females and males had a single mate during a male brooding period. Multilocus genotypes implicated four females in the adult population sample as contributors of eggs to the broods of collected males, but there was no evidence for multiple mating by females. Based on genotypic data from the progeny arrays, two loci were linked tightly and the recombination rate appeared to be approximately 10-fold higher in females than in males. The utility of linked loci for parentage analyses is discussed.

Apparently monogamous animals often prove, upon genetic inspection, to mate polygamously. Seahorse males provide care in a brood pouch. An earlier genetic study of the Western Australian seahorse demonstrated that males mate with only one female for each particular brood. Here we investigate whether males remain monogamous in sequential pregnancies during a breeding season. In a natural population we tagged males and sampled young from two successive broods of 14 males. Microsatellite analyses of parentage revealed that eight males re‐mated with the same female, and six with a new female. Thus, in this first study to document long‐term genetic monogamy in a seahorse, we show that switches of mates still occur. Polygynous males moved greater distances between broods, and tended to have longer interbrood intervals, than monogamous males, suggesting substantial costs associated with the breaking of pair bonds which may explain the high degree of social monogamy in this fish genus.

The phenomenon of male pregnancy in the family Syngnathidae (seahorses, pipefishes, and sea dragons) undeniably has sculpted the course of behavioral evolution in these fishes. Here we explore another potentially important but previously unrecognized consequence of male pregnancy: a predisposition for sympatric speciation. We present microsatellite data on genetic parentage that show that seahorses mate size-assortatively in nature. We then develop a quantitative genetic model based on these empirical findings to demonstrate that sympatric speciation indeed can occur under this mating regime in response to weak disruptive selection on body size. We also evaluate phylogenetic evidence bearing on sympatric speciation by asking whether tiny seahorse species are sister taxa to large sympatric relatives. Overall, our results indicate that sympatric speciation is a plausible mechanism for the diversification of seahorses, and that assortative mating (in this case as a result of male parental care) may warrant broader attention in the speciation process for some other taxonomic groups as well.ince the modern synthesis of evolutionary biology, the prevailing belief has been that most speciation events occur as a consequence of geographic barriers to gene flow (1, 2). However, in recent years a growing body of theoretical studies has established that sympatric speciation is possible and may be more common than thought previously (3-8). Nevertheless, there still exists a dearth of empirical systems in which sympatric speciation seems a likely explanatory mechanism (reviewed in ref. 8). The most convincing examples of sympatric speciation involve host-race formation by species such as Rhagoletis flies (9, 10) or pea aphids (8, 11) and ecological speciation in closed environments by taxa such as sticklebacks (12) or cichlids (13). Speciation in these types of systems probably involves the simultaneous evolution of assortative mating and phenotypic divergence through disruptive selection. Recent theoretical models show that such complex scenarios are plausible under biologically realistic conditions (5, 6, 14-16).The simplest situation favoring sympatric divergence occurs when both assortative mating and disruptive selection operate on the same phenotypic character (3,(17)(18)(19). Thus, if assortative mating appears in a population, even for reasons entirely unrelated to the speciation process, a lineage may in principle become predisposed to speciate whenever appropriate selective conditions arise. This model seems particularly feasible when mate choice involves ecologically important traits, which are likely to be the targets of selection, such as body size or habitat preference (3). This simplest scenario of sympatric speciation has not been empirically documented yet. Here we investigate the possibility that such a situation may have been important in the diversification of seahorses.This line of research was inspired by empirical field observations suggesting that seahorses mate assortatively by body size (20). Such ma...

A central issue in the development of marine research and monitoring programs is the identification of robust methodologies aimed at detecting spatial and temporal changes in abundance, diversity, and biomass of faunal assemblages (e.g., Maxwell and Jennings 2005;Cheal et al. 2008;Murphy and Jenkins 2010). Decisions on how to assess these metrics are initially based on the type of information required, what specific indices must be measured, the level of precision required to detect change, the repeatability of the method, and the environmental conditions under which assessments will take place (Connell et al. 1998;Willis et al. 2000;Smale et al. 2011). Importantly, the human capital and financial resources available to collect data must also be considered, as costs associated with different data collection techniques can vary substantially . However, for long-term monitoring projects technological advancements, scientific innovations, sporadic funding, and changes in the availability of staff expertise often mean that the most suitable assessment methods change through time (Murphy and Jenkins 2010). This may result in time-series datasets that are collected using several techniques. To ensure that trends in data are not attribut- AbstractRobust assessments of abundance and diversity are essential components of research programs aimed at detecting changes in marine fish assemblages through space and time. This study examined the comparability of Underwater Visual Census (UVC), and Diver Operated stereo-Video (Stereo-DOV) datasets collected across a wide latitudinal range (15°) on coral reefs and temperate rocky shores. There were some differences between methods with regards to both species richness and abundance, with UVC consistently recording higher measures of species richness. Differences were most pronounced at tropical locations where these measures were high. Differences in the characteristics of fish assemblages were primarily driven by UVC differentiating between scarid and pomacentrid species and detecting more cryptic species. When examined at higher taxonomic or functional levels however, there was greater comparability between the assemblages recorded by each method, particularly in temperate locations. The UVC method also recorded higher abundances of species targeted by fishers in tropical/sub-tropical locations, and subsequently obtained a much higher proportion of length measurements for these species. Data collected using stereo-DOV took 2-3 times longer to obtain than with UVC due to extensive post-processing time required by the stereo-DOV method. This study shows that data collected by the two methods are most comparable in temperate locations, or when examined at higher taxonomic/functional levels. Comparisons should however be more cautious in higher diversity locations, or when assessing at finer taxonomic resolution. When assessing the suitability of either method, availability of time, funding, and relevant expertise should be primary considerations.