Ecological correlates of range shifts of Late Pleistocene mammals

Understanding and predicting how species' distributions will shift as climate changes are central questions in ecology today. The late Quaternary of North America represents a natural experiment in which we can evaluate how species responded during the expansion and contraction of the glaciers. Here, we ask whether species' range shifts differ because of taxonomic affinity, life-history traits, body size or topographic heterogeneity and whether the species survived the megafaunal extinction. There was no difference in range shifts between victims and survivors of the megafaunal extinction. In general, the change in the size of a species' range is not well correlated with any of the ecological or life-history traits evaluated. However, there are significant relationships between some variables and the movements of the centroids of ranges. Differences in the distances shifted exist among orders, although this is probably a result of body size differences as larger bodied species show larger shifts. Although there are a few exceptions, the distance that species shifted their range was weakly correlated with life-history traits. Finally, species in more topographically heterogeneous areas show smaller shifts than species in less-diverse areas. Overall, these results indicate that when trying to predict species range shifts in the future, body size, lifespan and the topographic relief of the landscape should be taken into account.     

Ovulation mode modifies paternity monopolization in mammals

There are two forms of ovulation: spontaneous and induced. As copulation triggers ovulation for induced ovulators, males can predict the timing of ovulation and may have greater paternity monopolization than spontaneous ovulators. However, this prediction has never, to my knowledge, been tested. Using a cross-species comparison I examined the percentage of offspring sired within a litter (single paternity) and in social species the percentage of offspring sired by the dominant male (alpha paternity). My results indicate that ovulation mode alters the ability of males to monopolize paternity, with males of induced ovulators having higher single paternity and greater alpha paternity where male–female association is intermittent.     

Subordinate male meerkats prospect for extra-group paternity: alternative reproductive tactics in a cooperative mammal

In cooperatively breeding species, subordinates typically suffer strong constraints on within-group reproduction. While numerous studies have highlighted the additional fitness benefits that subordinates might accrue through helping, few have considered the possibility that subordinates may also seek extra-group matings to improve their chances of actually breeding. Here, we show that subordinate males in cooperative meerkat, Suricata suricatta, societies conduct frequent extraterritorial forays, during periods of peak female fertility, which give rise to matings with females in other groups. Genetic analyses reveal that extra-group paternity (EGP) accrued while prospecting contributes substantially to the reproductive success of subordinates: yielding the majority of their offspring (approx. 70%); significantly reducing their age at first reproduction and allowing them to breed without dispersing. We estimate that prospecting subordinates sire 20-25% of all young in the population. While recent studies on cooperative birds indicate that dominant males accrue the majority of EGP, our findings reveal that EGP can also arise from alternative reproductive tactics employed exclusively by subordinates. It is important, therefore, that future attempts to estimate the fitness of subordinate males in animal societies quantify the distribution of extra-group as well as within-group paternity, because a substantial proportion of the reproductive success of subordinates may otherwise go undetected.     

Parentage assignment and extra-group paternity in a cooperative breeder: the Seychelles warbler (Acrocephalus sechellensis)

We describe the development and initial application of a semiautomated parentage testing system in the Seychelles warbler (Acrocephalus sechellensis). This system used fluorescently labelled primers for 14 polymorphic microsatellite loci in two multiplex loading groups to genotype efficiently over 96% of the warbler population on Cousin island. When used in conjunction with the program CERVUS, this system provided sufficient power to assign maternity and paternity within the Seychelles warbler, despite the complications associated with its cooperative breeding system and a relatively low level of genetic variation. Parentage analyses showed that subordinate 'helper' females as well as the dominant 'primary' females laid eggs in communal nests, indicating that the Seychelles warbler has an intermediate level of female reproductive skew, in between the alternative extremes of helper-at-the-nest and joint nesting systems. Forty-four per cent of helpers bred successfully, accounting for 15% of all offspring. Forty per cent of young resulted from extra-group paternity.     

Polygynandry, extra-group paternity and multiple-paternity litters in European badger (Meles meles) social groups

The costs and benefits of natal philopatry are central to the formation and maintenance of social groups. Badger groups, thought to form passively according to the resource dispersion hypothesis (RDH), are maintained through natal philopatry and delayed dispersal; however, there is minimal evidence for the functional benefits of such grouping. We assigned parentage to 630 badger cubs from a high-density population in Wytham Woods, Oxford, born between 1988 and 2005. Our methodological approach was different to previous studies; we used 22 microsatellite loci to assign parent pairs, which in combination with sibship inference provided a high parentage assignment rate. We assigned both parents to 331 cubs at > or = 95% confidence, revealing a polygynandrous mating system with up to five mothers and five fathers within a social group. We estimated that only 27% of adult males and 31% of adult females bred each year, suggesting a cost to group living for both sexes. Any strong motivation or selection to disperse, however, may be reduced because just under half of the paternities were gained by extra-group males, mainly from neighbouring groups, with males displaying a mixture of paternity strategies. We provide the strongest evidence to date for multiple-paternity litters, and for the first time show that within-group and extra-group males can sire cubs in the same litter. We investigate the factors that may play a role in determining the degree of delayed dispersal and conclude that the ecological constraints hypothesis, benefits of philopatry hypothesis, and life history hypothesis may all play a part, as proposed by the broad constraints hypothesis.     

Group structure, mating system and extra-group paternity in the co-operatively breeding White-breasted Thrasher Ramphocinclus brachyurus

Avian co-operative breeders show a diverse range of social and reproductive systems. Here we combined microsatellite genotyping with field observations over three consecutive breeding seasons to investigate the social structure and mating system of the White-breasted Thrasher Ramphocinclus brachyurus . Co-operative breeding was facultative in this species, with approximately one-third of nests having helpers. Breeding groups comprised a pair of breeding adults and up to three helpers of either sex. Within co-operative groups, age was associated with parentage in both sexes. Helpers were retained offspring and either rarely or never achieved parentage in current broods. There was no evidence of egg dumping and a relatively small percentage of chicks (7.5%, n  = 67) were fathered by males from outside the co-operative group. The White-breasted Thrasher is a globally Endangered species with a very small and declining population. A captive breeding programme for this species is not recommended at present, but may become necessary in the future, and any such programme should take account of our findings regarding breeding behaviour and group structure.     

Social structure influences extra-pair paternity in socially monogamous mammals

Using the genetic estimates of paternity available for 22 species of socially monogamous mammals, we investigated the impact of the social structure and of the type of pair bonding on the interspecific variations of extra-pair paternity rates. To this purpose, we classified species in three categories of social structure—solitary, pair or family-living species—and in two categories of pair bonding—intermittent or continuous. We show that interspecific variations of extra-pair paternity rates are better explained by the social structure than by the type of pair bonding. Species with intermittent and continuous pair bonding present similar rates of extra-pair paternity, while solitary and family-living species present higher extra-pair paternity rates than pair-living species. This can be explained by both higher male–male competition and higher female mate choice opportunities in solitary and family-living species than in pair-living species.     

High levels of extra-group paternity in a population of Australian magpies Gymnorhina tibicen: evidence from microsatellite analysis

Breeding systems vary widely in birds, from monogamous pairs through to complex group systems where subordinates assist breeding individuals to rear young each season. The Australian magpie varies geographically both in plumage patterns and social organization. Some populations of both eastern and western plumage forms are plural breeders with group size varying from three to over 15 mature individuals. This study used variation at microsatellite loci to determine the level of extra-group paternity in a population of the western form near Perth in Western Australia. Extra-group paternity was the highest recorded for any bird species to date (82%) and indicates that few offspring within a territory are sired by the social partner of the female. In addition, the data indicated that nearly 10% of juveniles were not the genetic offspring of any female within their territory, suggesting some intraspecific brood parasitism. Taken together, these findings are remarkable considering the highly territorial nature of the species and the extent of territorial defence practised by all members of the group towards extra-group conspecifics during daylight hours.     

Ecological correlates of body size in gamasid mites parasitic on small mammals: abundance and niche breadth

We studied ecological correlates of body size (abundance and niche breadth) in gamasid mites parasitic on small mammals in 28 regions of the Palearctic. We predicted that smaller species would be characterized by higher abundance than larger species, all else (e.g. host species) being equal. We also predicted that host specificity of mites would decrease (that is, number of host species they use would increase) with an increase in their body size. We focused on mites collected from host bodies that include a) species that feed solely on host’s blood (obligate exclusive haematophages), b) species that feed on both host’s blood and small arthropods (obligate non‐exclusive haematophages), and c) facultative haematophages. We expected that the relationship between body size and abundance and/or host specificity would be more pronounced in obligate exclusively haematophagous mites than for obligate non‐exclusively and facultative haematophagous mites. Across all mite species across regions, mean abundance correlated negatively with body size. The same was true for obligate haematophagous species, but not for facultative haematophages. When mite communities on the same host in a location were considered, the negative body mass–abundance relationship was found in only 3 of 44 communities. Nevertheless, a meta‐analytic (across host species) estimate of the slope of this relationship appeared to be significantly negative. No significant relationship between mite body size and host specificity was found in the analyses across all mite species as well as in obligate exclusive or obligate non‐exclusive haematophages. However, the number of hosts used by facultative haematophagous mites decreased significantly with an increase in their body size. We explain the relationships between morphological (body size) and ecological (abundance and niche breadth) properties of ectoparasites by their interactions with hosts or physical environment.     

Ecological constraints on extra-pair paternity in the bluethroat

The mating system of the bluethroat (Luscinia s. svecica) involves a high level of sperm competition, and consequently a high frequency of extra-pair paternity (EPP). There is considerable variation in the frequency of EPP. Over the course of ten study years in a population in Norway, the frequency has fluctuated between 7% and 33% of young, and 8% and 76% of broods. In this paper, we address the issue of whether ecological factors can explain some of the variation in EPP between years and broods. Factors include breeding density, breeding synchrony and two meteorological variables (ambient temperature and precipitation) during the period of peak female fertility. There were no significant relationships between annual averages of the four variables and the annual level of EPP, but the statistical power of these tests was low, due to a restricted sample (n=10 years). Focussing on individual broods, none of the factors had significant effects when including all broods in the analyses (including those with zero EPP). When limiting the analyses to broods with one or more extra-pair offspring, morning temperature had a significant effect on the frequency of EPP. When the temperature was low during the peak of the fertile period, EPP occurred less frequently. Male extra-pair behaviour was not generally constrained by synchrony between the fertile periods of the social mate and the extra-pair mate, but for a subgroup of males ("unattractive males") there appeared to be a trade-off between mate guarding and pursuing extra-pair copulations. Our results indicate that ecological conditions have no influence on whether or not a brood will contain extra-pair offspring, but when EPP does occur, its frequency is influenced by air temperature. Possibly, there is a causal relationship between weather conditions and the frequency of extra-pair encounters in this species. The breeding season is initiated at a phenologically early stage, when large parts of the territories are still covered with snow, and cold weather conditions may force the birds to devote most of their time to maintenance and thereby constrain sexual activities.     

Neuronal correlates of corticalization in mammals: a theory

The cerebral cortex of mammals has been found to be uniformly organized, and to be composed of elementary processing units or modules having an essentially constant number of neurons. In the present paper the hypothesis is put forward that the relative proportion of local circuit neurons (LCNs) within a module reflects the evolutionary level of corticalization of a mammal. The modules, in turn, are interconnected so as to form basic neuronal networks or columns with a species-specific width varying from 90 to 310 microns. A mathematical formalism is presented from which the hypothetical ratio between LCNs and projection neurons, as well as the size of the cortical column and the number of modular units that it contains, can be calculated.     

Early sibling aggression in mammals and its hormonal correlates

Early sibling aggression is a widespread phenomenon in birds. Ornithologists distinguish species with "obligate" and "facultative" siblicide. Sibling aggression was described in some mammal species: the domestic pig (Sus scrofa), the spotted hyena (Crocuta crocuta), the Eurasian lynx (Lynx lynx), and the Iberian lynx (L. par-dinus). In all of them, sibling aggression corresponds well with the "facultative" siblicide model in birds. Sibling aggression was observed at the age of 36-64 days in both lynx species. It is usually restricted to a single fight and can change the hierarchical structure and growth rate of the kittens. In the spotted hyena and the domestic pig, the frequency and intensity of aggressive interactions between siblings are strongest during the first days of postnatal ontogeny and then decrease gradually. The newborns of these species are much developed than newborn lynx kittens. Usually adult lynx females, in contrast to hyenas and pigs, try to stop sibling fights. This is probably related to the larger parental investment at the time of the fight in lynxes (a kitten's body weight is about 10% of the mother's) than in pigs (0.5%) and hyenas (1.9%). Sibling aggression in spotted hyenas could be related to the high level of androstenedione and is not related to testosterone concentration. In the Eurasian lynx, female sibs attack their littermates slightly more often than male sibs do, and sibling aggression is not testosterone-dependent. Hormones secreted by the adrenal glands may play an important role in this phenomenon. The data available so far, however, do not positively confirm the presence of hormonal trigger effects in mammal sibling aggression.     

Demographic correlates of paternity confidence and pregnancy outcomes among Albuquerque men

We examine the demographic correlates of paternity confidence, or men's assessment of the likelihood that they are the genetic father of a particular child. Evolutionary theory predicts that men will provide less parental investment for putative genetic offspring who are unlikely to be their actual offspring, but confidence of paternity has not been as extensively examined as its importance would merit. Using self-reported data on paternity confidence in 3,360 pregnancies reported by men living in Albuquerque, New Mexico, we find that low paternity confidence is more common among unmarried couples and for unplanned pregnancies. We also find that men are more likely not to state paternity confidence (i.e., they refuse to answer the question) if a pregnancy is unplanned. We additionally examine the pregnancy outcomes associated with confidence of paternity. We find that low paternity confidence pregnancies are significantly more likely to be aborted, and pregnancies for which paternity confidence is unstated are more likely to be aborted or to miscarry. Both abortion and miscarriage are associated with unmarried couples, with unplanned pregnancies, and with couples who have fewer children together.     

Ecologic correlates of Toxoplasma gondii exposure in free-ranging neotropical mammals

A serologic survey for Toxoplasma gondii in 18 free-ranging forest mammal species (n = 456) in French Guiana was undertaken with a direct agglutination test. Serum antibody prevalence varied from 0-71%. The relationships between ecologic features of the species and seroprevalence were investigated. Terrestrial mammals were significantly more exposed to T. gondii than other mammals. This result is concordant with oral exposure to T. gondii related to ground dwelling behavior and/or carnivory.     

Patterns and correlates of extrapair paternity in American redstarts (Setophaga ruticilla)

We examined correlates and hypotheses pertaining to extrapairfertilizations in socially monogamous American redstarts (Setophagaruticilla). DNA fingerprinting revealed extrapair fertilizationin 59% of broods (19 of 32), involving 40% of nestlings (43of 108). Fewer broods than expected had mixed paternity, asdetermined from a binomial distribution of extrapair young inthe population. This result is consistent with the "good genes"hypothesis, but not with the "genetic diversity" hypothesis.There was a negative association between the age of putativefathers and the proportion of extrapair young in their broods.Irrespective of age, males with prior residency were cuckoldedless often than males new to the study area. Extrapair fatherswere' immediate neighbors in 7 of 10 cuckolded broods whereall neighbors were sampled. Males were more likely to sire offspringin the territories of younger neighbors than in those of olderneighbors. Plumage characteristics of adult males, breedingsynchrony of females, and breeding densities were not significantlyassociated with cuckoldry. Realized reproductive gain from cuckoldrywas small because of high nest predation in our area. Extrapairfertilizations allowed one-quarter of males whose own nestshad failed to achieve some reproductive success. Only 2 of 17males whose own nests were successful also had extrapair young.There was no egg dumping by females. We conclude that male ageand prior residency were predictors of cuckoldry in Americanredstarts. In the context of the heavy predation experiencedby our birds, extrapair fertilizations allowed many males tosalvage some reproductive success and did not increase the varianceof success across males     

Ecological specialization in fossil mammals explains Cope's rule

Cope's rule is the trend toward increasing body size in a lineage over geological time. The rule has been explained either as passive diffusion away from a small initial body size or as an active trend upheld by the ecological and evolutionary advantages that large body size confers. An explicit and phylogenetically informed analysis of body size evolution in Cenozoic mammals shows that body size increases significantly in most inclusive clades. This increase occurs through temporal substitution of incumbent species by larger-sized close relatives within the clades. These late-appearing species have smaller spatial and temporal ranges and are rarer than the incumbents they replace, traits that are typical of ecological specialists. Cope's rule, accordingly, appears to derive mainly from increasing ecological specialization and clade-level niche expansion rather than from active selection for larger size. However, overlain on a net trend toward average size increase, significant pulses in origination of large-sized species are concentrated in periods of global cooling. These pulses plausibly record direct selection for larger body size according to Bergmann's rule, which thus appears to be independent of but concomitant with Cope's.     

Ecological correlates of anuran exercise physiology

Summary Studies of exercise physiology of anuran amphibians have led to the suggestion that there is a dichotomy between species that depend upon movement to escape from predators and species that utilize static defenses. This generalization has been based upon a limited taxonomic survey and it contrasts with morphological, ecological, and behavioral studies that have revealed diverse and complex interrelationships among these features of anuran biology. We tested the hypothesis of a dichotomy of physiological types among anurans by measuring aerobic and anaerobic metabolism during maximum exercise for 17 species representing seven families and a variety of ecological types and locomotor modes. All degrees of dependence upon aerobic and anaerobic power input were found among the 17 species and the variation did not follow phylogenetic divisions. No single, simple prediction of the predominant source of power utilized for activity by the anurans we studied is possible. Predator avoidance behavior was not significantly correlated with the metabolic pattern. Predatory mode (active versus passive searchers) and mode of locomotion (non-jumpers versus jumpers) were correlated with dependence upon aerobic energy production and with each other. Reproductive behavior is probably another associated factor. The diversity of modes of power input among anurans is great and is intimately linked with numerous features of a species' biology. Single-factor explanations of this physiological characteristic are not appropriate.