Aggression and spatial positioning of kin and non-kin fish in social groups

Group-living animals must share space and resources with group mates, who can be either kin or non-kin, and it is often unclear how competitive or cooperative group members should be. In a group-living cichlid, we show that co-habiting females are less aggressive to their female kin (relative to non-kin) despite living at equivalent distances to one another. This pattern was not detected among co-habiting males, revealing that kin-directed social behavior can differ between the sexes.Group-living animals are faced with the challenge of sharing space and local resources amongst group members who may be either relatives or non-relatives. Individuals may reduce the inclusive fitness costs they incur from competing with relatives by either reducing their levels of aggression toward kin, or by maintaining physical separation between kin. In this field study, we used the group-living cichlid Neolamprologus multifasciatus to examine whether within-group aggression is reduced among group members that are kin, and whether kin occupy different regions of their group's territory to reduce kin competition over space and local resources. We determined the kinship relationships among cohabiting adults via microsatellite genotyping and then combined these with spatial and behavioral analyses of groups in the wild. We found that aggressive contests between group members declined in frequency with spatial separation between their shelters. Female kin did not engage in aggressive contests with one another, whereas non-kin females did, despite the fact these females lived at similar distances from one another on their groups' territories. Contests within male-male and male-female dyads did not clearly correlate with kinship. Non-kin male-male and male-female dyads lived at more variable distances from one another on their territories than their corresponding kin dyads. Together, our study indicates that contests among group members can be mediated by relatedness in a sex-dependent manner. We also suggest that spatial relationships can play an important role in determining the extent to which group members compete with one another

Patterns of sex-biased dispersal are consistent with social and ecological constraints in a group-living cichlid fish

BackgroundSex-biased dispersal is a common and widespread phenomenon that can fundamentally shape the genetic structure of the social environments in which animals live. For animals that live in and move between social groups, sex-biased dispersal can result in an asymmetry in the degree of relatedness among cohabiting males and females, which can have strong implications for their social evolution. In this study, we measured the relatedness structure within and across groups of a wild population of Neolamprologus multifasciatus, a highly-social, shell-dwelling cichlid fish endemic to Lake Tanganyika, East Africa. In total, we genotyped 812 fish from 128 social groups at 20 microsatellite loci. Neolamprologus multifasciatus live at high densities, and also experience strong ecological constraints on free movement throughout their habitat. At the same time, they exhibit sex differences in the degree of reproductive competition within their groups and this makes them an excellent model system for studying the factors associated with sex-biased dispersal.ResultsSocial groups of N. multifasciatus consist of multiple males and females living together. We found that cohabiting females were unrelated to one another (Lynch-Ritland estimates of relatedness = 0.045 ± 0.15, average ± SD), while males shared much higher, albeit variable, levels of relatedness to other males in their groups (0.23 ± 0.27). We uncovered a pronounced decline in relatedness between males living in separate groups as the spatial separation between them increased, a pattern that was not evident in females. Female dispersal was also markedly constrained by the distribution and availability of nearby territories to which they could emigrate.ConclusionsOur results indicate female-biased dispersal in N. multifasciatus. Our study also highlights how the spatial distribution of suitable dispersal destinations can influence the movement decisions of animals. We also emphasize how sex-biased dispersal can influence the relatedness structure of the social environment in which individuals interact and compete with one another.publishe

Genome-Based Species Diversity Assessment in the Pseudomonas chlororaphis Phylogenetic Subgroup and Proposal of Pseudomonas danubii sp. nov. Isolated from Freshwaters, Soil, and Rhizosphere

The Pseudomonas chlororaphis phylogenetic subgroup of species, within the Pseudomonas fluorescens group, currently includes seven bacterial species, all of which have environmental relevance. Phylogenomic analyses help clarify the taxonomy of strains in the group and allow for precise identification. Thirteen antibiotic-resistant strains isolated in a previous study from nine different sampling sites in the Danube River were suspected to represent a novel species and are investigated taxonomically in the present study, together with four other strains isolated from the Woluwe River (Belgium) that were phylogenetically closely related in their rpoD gene sequences. The strains were characterized phenotypically, chemotaxonomically (fatty acid composition and main protein profiles), and phylogenetically. They could not be assigned to any known Pseudomonas species. Three genomes of representative strains were sequenced and analyzed in the context of the genome sequences of closely related strains available in public databases. The phylogenomic analysis demonstrates the need to differentiate new genomic species within the P. chlororaphis subgroup and that Pseudomonas piscis and Pseudomonas aestus are synonyms. This taxonomic study demonstrates that 14 of the characterized isolates are members of the Pseudomonas_E protegens_A species in the GTDB taxonomy and that they represent a novel species in the genus Pseudomonas, for which we propose the name Pseudomonas danubii sp. nov. with strain JDS02PS016T (=CECT 30214T = CCUG 74756T) as the type strain. The other three strains (JDS08PS003, rDWA16, and rDWA64) are members of the species Pseudomonas_E protegens_B in the GTDB taxonomy and need further investigation for proposal as a new bacterial species.This study was funded by the Spanish Ministry of Science and Innovation MICIN/AEI, 10.13039/501100011033, project PID2020-119449RB-I00 (to MG and EGV).Peer reviewe

Parentage analysis across age cohorts reveals sex differences in reproductive skew in a group-living cichlid fish, Neolamprologus multifasciatus

Group-living animals are often faced with complex reproductive decisions, namely how to partition within-group reproduction, how to obtain extra-group reproduction, and how these two means of reproduction should be balanced. The solutions to these questions can be difficult to predict because ecological conditions can affect the scopes for within-group and extra-group reproduction in complex ways. For example, individuals that are restricted from moving freely around their habitats may have limited extra-group reproductive opportunities, but at the same time, groups may live in close proximities to one another, which could potentially have the opposite effect. The group-living cichlid fish, Neolamprologus multifasciatus, experiences such ecological conditions, and we conducted an intensive genetic parentage analysis to investigate how reproduction is distributed within and among groups for both males and females. We found that cohabiting males live in ‘high-skew’ societies, where dominant males monopolize the majority of within-group reproduction, while females live in ‘low-skew’ societies, where multiple females can produce offspring concurrently. Despite extremely short distances separating groups, we inferred only very low levels of extra-group reproduction suggesting that subordinate males have very limited reproductive opportunities. A strength of our parentage analysis lies in its inclusion of individuals that spanned a wide age range, from young fry to adults. We outline the logistical circumstances when very young offspring may not always be accessible to parentage researchers, and present strategies to overcome the challenges of inferring mating patterns from a wide age range of offspring.publishe