Jeff A. Graves

Microsatellite and mtDNA analysis of the population structure of grey seals (Halichoerus grypus) from three breeding areas in the Baltic Sea

The growing number of grey seals in the Baltic Sea has led to a dramatic increase in interactions between seals and fisheries. The conflict has become such a problem that hunting was introduced in Finland in 1998 and the Swedish Environment Protection Agency recommended a cull of grey seals starting in 2001. Culling has been implemented despite the lack of data on population structure. Low levels of migration between regions would mean that intensive culling in specific geographic areas would have disproportionate effects on local population structure and genetic diversity. We used eight microsatellite loci and a 489xa0bp section of the mtDNA control region to examine the genetic variability and differentiation between three breeding sites in the Baltic Sea and two in the UK. We found high levels of genetic variability in all sampled Baltic groups for both the microsatellites and the control region. There were highly significant differences in microsatellite allele frequencies between all three Baltic breeding sites and between the Baltic sites and the UK sites. However, there were no significant differences in mtDNA control region haplotypes between the Baltic sites. This genetic substructure of the Baltic grey seal populations should be taken into consideration when managing the seal population to prevent the hunting regime from having an adverse effect on genetic diversity by setting hunting quotas separately for the different subpopulations.

Reproductive partitioning in communally breeding guira cuckoos, Guira guira

Guira cuckoos, Guira guira, exhibit a rare polygynandrous reproductive system with groups containing several male and female breeders, allowing for important tests of reproductive skew models. Female reproductive strategies involve leaving the group, varying clutch size, egg ejection and infanticide, among others. Here we examined the predictions of reproductive skew models relative to reproductive partitioning among females in groups. We used yolk protein electrophoresis to identify individual females’ eggs in joint nests. We found that reproductive partitioning favors early-laying females, which lay and incubate more eggs than females that begin laying later. Because the female that lays first tends to switch between repeated nesting bouts, and females do not always contribute eggs to each bout, female reproductive success tends to equalize within groups over time. The pattern of reproductive partitioning differs from that described for anis, another crotophagine joint-nester. We calculated reproductive skew indices for groups in 2xa0years, for both laying and incubation, as well as an overall population value. These were compared to random skew generated by simulations. Varying degrees of skew were found for different groups, and also across sequential nesting bouts of the same groups. Overall, however, skew did not deviate from random within the population. Nests that reached incubation tended to have lower skew values during the laying phase than nests terminated due to ejection of all eggs followed by desertion. Groups had higher reproductive skew indices in their first nesting bout of the season, and these nests frequently failed. These results illustrate the importance of social organization in determining not only individual, but group success in reproduction, and highlight the flexibility of vertebrate social behavior.

Vigor and skill in the acrobatic mating displays of a Neotropical songbird

Animal social behaviors are often mediated by signals that provide information about signaler attributes. Although some signals are structurally simple, others are temporally dynamic and multifaceted. In such cases, exaggeration of some display components is likely to curtail the expression of others. We quantified features of the acrobatic, multimodal “leap display” of blue-black grassquits (Volatinia jacarina), which appears to entail moderate-to-high performance levels in terms of vigor and skill. We video recorded and quantified leap parameters (height, duration, rotation angle, launch velocity, and number of wing beats) and assessed how these parameters covaried with each other and with vocal parameters, display rates, and body mass index. Our analyses revealed correlations among multiple performance variables: leap height, duration, launch velocity, and number of wing beats. Leap height also correlated positively with song duration. By contrast, no leap parameters covaried with rotation angle. Our analyses also revealed a trade-off in vigor and skill-based leap attributes: birds with a lower body mass index showed a negative relationship between leap heights and the proportion of displays that included leaps (vs. perched vocalizations only). Our results identify directions of display evolution subject to mechanical or timing constraints and provide evidence that display attributes that emphasize vigor and skill may limit one another. Our results also support a key expectation of handicap models of display evolution, which is that costs of display execution should be borne disproportionately by signalers of lower quality.

Shift of grey seal subspecies boundaries in response to climate, culling and conservation

Identifying the processes that drive changes in the abundance and distribution of natural populations is a central theme in ecology and evolution. Many species of marine mammals have experienced dramatic changes in abundance and distribution due to climatic fluctuations and anthropogenic impacts. However, thanks to conservation efforts, some of these species have shown remarkable population recovery and are now recolonizing their former ranges. Here, we use zooarchaeological, demographic and genetic data to examine processes of colonization, local extinction and recolonization of the two northern European grey seal subspecies inhabiting the Baltic Sea and North Sea. The zooarchaeological and genetic data suggest that the two subspecies diverged shortly after the formation of the Baltic Sea approximately 4200 years bp, probably through a gradual shift to different breeding habitats and phenologies. By comparing genetic data from 19th century pre‐extinction material with that from seals currently recolonizing their past range, we observed a marked spatiotemporal shift in subspecies boundaries, with increasing encroachment of North Sea seals on areas previously occupied by the Baltic Sea subspecies. Further, both demographic and genetic data indicate that the two subspecies have begun to overlap geographically and are hybridizing in a narrow contact zone. Our findings provide new insights into the processes of colonization, extinction and recolonization and have important implications for the management of grey seals across northern Europe.

One Species or Two? Vicariance, Lineage Divergence and Low mtDNA Diversity in Geographically Isolated Populations of South Asian River Dolphin

Despite their endangered status, the taxonomic relationship between the two geographically isolated South Asian river dolphin populations has never been comprehensively assessed and remains contentious. Here we present the first dedicated evaluation of the molecular phylogenetic relationship between the Indus (Platanista gangetica minor) and Ganges (Platanista gangetica gangetica) River dolphins using mitochondrial DNA from the control region and cytochrome b, extracted from museum specimens. The 458xa0bp partial control region sequences from 26 Indus River dolphin samples exhibited no variation. Only six haplotypes were identified in the 31 (18 Indus; 13 Ganges) complete (856xa0bp) control region sequences obtained, none were shared between subspecies, and there were five fixed differences between them. Similarly low genetic diversity was found in a 541xa0bp section of the cytochrome b gene (nu2009=u200929). The lack of shared haplotypes and fixed differences resulted in ΦST for the partial control region sequences of 0.932 (pu2009<u20090.0001) and FST of 0.843 (pu2009<u20090.0001), indicating the long-term absence of gene flow and clear genetic differentiation between the two geographically isolated populations. An externally calibrated molecular clock estimated that Indus and Ganges dolphins diverged around 550,000xa0years ago (95xa0% posterior probability 0.13–1.05xa0million years ago), possibly when dolphins from the Ganges dispersed into the Indus during drainage capture.

Multimodal flight display of a neotropical songbird predicts social pairing but not extrapair mating success

Models of sexual selection predict that socially monogamous females may gain direct or indirect (genetic) benefits by mating with multiple males. We addressed current hypotheses by investigating how, in the socially monogamous blue-black grassquit (Volatinia jacarina), male courtship and territory quality varied with social and extrapair paternity. Males of this tropical granivorous passerine exhibit multimodal displays integrating motor (leap displays) and acoustic components. Across 3xa0years, we found that extrapair paternity ranged from 8 to 34xa0% of all nestlings and from 11xa0to 47xa0% of all broods. Extrapair and socially paired male territories had similar seed densities. Females preferred to pair socially with males executing higher leaps, but no other male display characteristic associated with paternity loss and extrapair fertilizations. Extrapair and social mates did not differ in genetic similarity to female partners nor in inbreeding levels. Additionally, inbreeding and body condition of extrapair and within-pair nestlings did not differ. Thus, not only did we reject the direct benefits hypothesis for extrapair copulations, but our results also did not support the additive and nonadditive genetic benefits hypotheses. Instead, we found support for benefits through selection of potentially “good fathers,” specifically for females that chose to pair socially with males exhibiting enhanced performance in their displays.Significance statementMultiple mating by females is intriguing because resulting advantages seem improbable. However, access to resources, genetic compatibility with the sexual partner and good gene transmission to the offspring are possible explanations for this behavior in several animals, including socially monogamous species. We investigated potential benefits in a socially monogamous neotropical bird, the blue-black grassquit. Males attract females using a sexual display of repeated leap flights synchronized with a song. We found that when selecting social mates, females favor higher-leaping males, an attribute associated with enhanced body condition that could indicate the capacity for better parenting and also be inherited by the offspring. Yet, when choosing extrapair males, females did not appear to base choices on leap parameters, vocal attributes, and genetic compatibility. These results do not suggest benefits for multiple mating by females, but show that selection of males in good physical condition can influence choice for social mates.

Phylogenetic relationships in southern African Bryde’s whales inferred from mitochondrial DNA: further support for subspecies delineation between the two allopatric populations

Bryde’s whales (Balaenoptera edeni) are medium-sized balaenopterids with tropical and subtropical distribution. There is confusion about the number of species, subspecies and populations of Bryde’s whale found globally. Two eco-types occur off South Africa, the inshore and offshore forms, but with unknown relationship between them. Using the mtDNA control region we investigated the phylogenetic relationship of these populations to each other and other Bryde’s whale populations. Skin, baleen and bone samples were collected from biopsy-sampled individuals, strandings and museum collections. 97 sequences of 674xa0bp (bp) length were compared with published sequences of Bryde’s whales (nu2009=u20096) and two similar species, Omura’s (B. omurai) and sei (B. borealis) whales (nu2009=u20093). We found eight haplotypes from the study samples: H1–H4 formed a distinct, sister clade to pelagic populations of Bryde’s whales (B. brydei) from the South Pacific, North Pacific and Eastern Indian Ocean. H5–H8 were included in the pelagic clade. H1–H4 represented samples from within the distributional range of the inshore form. Pairwise comparisons of the percentage of nucleotide differences between sequences revealed that inshore haplotypes differed from published sequences of B. edeni by 4.7–5.5% and from B. brydei by 1.8–2.1%. Ten fixed differences between inshore and offshore sequences supported 100% diagnosability as subspecies. Phylogenetic analyses grouped the South African populations within the Bryde’s-sei whale clade and excluded B. edeni. Our data, combined with morphological and ecological evidence from previous studies, support subspecific classification of both South African forms under B. brydei and complete separation from B. edeni.