Kin recognition and incest avoidance in a group-living insect

Mate choice theories predict that animals evolved strategiesto mate with optimally genetically dissimilar partners, providingfitness benefits. In group-living species, when adults do notdisperse, assessment of relatedness between conspecifics canbe a key factor for choosing mates. Here, we report for thefirst time, kin recognition abilities and their implicationin mate choice in the gregarious cockroach, Blattella germanica(L.). Binary choice tests showed that females mated preferentiallywith nonsibling rather than with sibling males, thus avoidingincest. In addition, inbreeding induced an important decreaseof their reproductive success. Contrary to what could be expectedwhen females had the choice between a nonsibling strain memberand a nonstrain member, they did not avoid mating with distantlyrelated nonstrain members, and extreme outbreeding induced anincrease of their reproductive success. Furthermore, our matechoice experiments disentangled the influences of familiarityfrom those of relatedness and evidenced that kin discriminationwas based on genetic cues independently of familiarity. Phenotypematching was a plausible mechanism for kin recognition. Contraryto many insect species, body size was not a salient criterionfor mate choice and had no consequences on reproductive success.     

Intergroup transfer and incest avoidance in semifree-ranging barbary macaques (Macaca sylvanus) at Salem (FRG)

During a long-term study of social behavior of semifree-ranging Barbary macaques, data on group transfer and sexual behavior were collected. A large population containing five groups living in a 14.5 ha outdoor enclosure was studied. Demographic data on the whole population are available for a period of six years. Data on sexual behavior of members of one large group were collected, by both focal animal and ad libitum techniques, for a period of two years. Matrilineal kinship relations of all except the oldest members of this intensively studied group were known. Males changed groups most frequently between the ages of three and five years i.e., the time at which sexual maturity was reached. While more than 30% of all males three years old and older changed groups during the study period, many males remained members of their natal group even after reaching adulthood. However, sexual interactions, especially matings between close matrilineal relatives, were found to be almost absent, suggesting that Barbary macaques are not highly inbred as formerly supposed.     

Evidence for frequent incest in a cooperatively breeding mammal

As breeding between relatives often results in inbreeding depression, inbreeding avoidance is widespread in the animal kingdom. However, inbreeding avoidance may entail fitness costs. For example, dispersal away from relatives may reduce survival. How these conflicting selection pressures are resolved is challenging to investigate, but theoretical models predict that inbreeding should occur frequently in some systems. Despite this, few studies have found evidence of regular incest in mammals, even in social species where relatives are spatio-temporally clustered and opportunities for inbreeding frequently arise. We used genetic parentage assignments together with relatedness data to quantify inbreeding rates in a wild population of banded mongooses, a cooperatively breeding carnivore. We show that females regularly conceive to close relatives, including fathers and brothers. We suggest that the costs of inbreeding avoidance may sometimes outweigh the benefits, even in cooperatively breeding species where strong within-group incest avoidance is considered to be the norm.     

Causes and consequences of incest avoidance in the cooperatively breeding mole-rat, Cryptomys darlingi (Bathyergidae)

A number of social mole-rat species maintain a strong reproductive skew (only one breeding pair in the group) solely through incest avoidance. Incest avoidance probably evolved for one of two reasons, namely for actually maintaining a reproductive skew or, alternatively, to avoid high inbreeding depression. In the latter case a strong reproductive skew would result as a fortuitous by-product of the combination of a cloistral family life style of mole-rats and incest avoidance. We undertook breeding experiments in which the fertility of pairs of unrelated individuals were compared with that of pairs of double first cousins. Inbreeding depression was remarkably high and an accompanying model suggests that it may be sufficient to support the idea that strong incest avoidance evolved primarily to eliminate the costs of inbreeding and subsequently facilitated the evolution of reproductive skew.     

The nature of fisheries- and farming-induced evolution

Humans have a penchant for unintentionally selecting against that which they desire most. In fishes, unprecedented reductions in abundance have been associated with unprecedented changes in harvesting and aquaculture technologies. Fishing, the predominant cause of fish-population collapses, is increasingly believed to generate evolutionary changes to characters of import to individual fitness, population persistence and levels of sustainable yield. Human-induced genetic change to wild populations can also result from interactions with their domesticated counterparts. Our examination of fisheries- and farming-induced evolution includes factors that may influence the magnitude, rate and reversibility of genetic responses, the potential for shifts in reaction norms and reduced plasticity, loss of genetic variability, outbreeding depression and their demographic consequences to wild fishes. We also suggest management initiatives to mitigate the effects of fisheries- and farming-induced evolution. Ultimately, the question of whether fishing or fish farming can cause evolutionary change is moot. The key issue is whether such change is likely to have negative conservation- or socio-economic consequences. Although the study of human-induced evolution on fishes should continue to include estimates of the magnitude and rate of selection, there is a critical need for research that addresses short- and long-term demographic consequences to population persistence, plasticity, recovery and productivity.     

The evolution and functional diversification of animal microRNA genes

microRNAs （miRNAs） are an abundant class of-22 nucleotide （nt） regulatory RNAs that are pervasive in higher eukaryotic genomes. In order to fully understand their prominence in genomes, it is necessary to elucidate the molecular mechanisms that can diversify miRNA activities. In this review, we describe some of the many strategies that allow novel miRNA functions to emerge, with particular emphasis on how miRNA genes evolve in animals. These mechanisms include changes in their sequence, processing, or expression pattern; acquisition of miRNA^＊ functionality or antisense processing; and de novo gene birth. The facility and versatility of miRNAs to evolve and change likely underlies how they have become dominant constituents of higher genomes.     

Pathogen evolution under host avoidance plasticity

Host resistance consists of defences that limit pathogen burden, and can be classified as either adaptations targeting recovery from infection or those focused upon infection avoidance. Conventional theory treats avoidance as a fixed strategy which does not vary from one interaction to the next. However, there is increasing empirical evidence that many avoidance strategies are triggered by external stimuli, and thus should be treated as phenotypically plastic responses. Here, we consider the implications of avoidance plasticity for host–pathogen coevolution. We uncover a number of predictions challenging current theory. First, in the absence of pathogen trade-offs, plasticity can restrain pathogen evolution; moreover, the pathogen exploits conditions in which the host would otherwise invest less in resistance, causing resistance escalation. Second, when transmission trades off with pathogen-induced mortality, plasticity encourages avirulence, resulting in a superior fitness outcome for both host and pathogen. Third, plasticity ensures the sterilizing effect of pathogens has consequences for pathogen evolution. When pathogens castrate hosts, selection forces them to minimize mortality virulence; moreover, when transmission trades off with sterility alone, resistance plasticity is sufficient to prevent pathogens from evolving to fully castrate.     

Admixture between native and invasive populations may increase invasiveness of Mimulus guttatus

Self-fertilization and admixture of genotypes from different populations can have major fitness consequences in native species. However, few studies have addressed their potential roles in invasive species. Here, we used plants of Mimulus guttatus from seven native North American, three invasive Scottish and four invasive New Zealand populations to address this. We created seeds from self-fertilization, within-population outcrossing, between-population outcrossing within the same range, and outcrossing between the native and invasive ranges. A greenhouse experiment showed that native and invasive plants of M. guttatus suffered to similar degrees from inbreeding depression, in terms of asexual reproduction and biomass production. After outcrossing with plants from other populations, M. guttatus benefited from heterosis, in terms of asexual and sexual reproduction, and biomass production, particularly when plants from native and invasive populations were crossed. This suggests that, when novel genotypes of M. guttatus from the native North American range will be introduced to the invasive ranges, subsequent outcrossing with M. guttatus plants that are already there might further boost invasiveness of this species.     

Physiological regulation and functional significance of shade avoidance responses to neighbors

Plants growing in dense vegetations compete with their neighbors for resources such as water, nutrients and light. The competition for light has been particularly well studied, both for its fitness consequences as well as the adaptive behaviors that plants display to win the battle for light interception. Aboveground, plants detect their competitors through photosensory cues, notably the red:far-red light ratio (R:FR). The R:FR is a very reliable indicator of future competition as it decreases in a plant-specific manner through red light absorption for photosynthesis and is sensed with the phytochrome photoreceptors. In addition, also blue light depletion is perceived for neighbor detection. As a response to these light signals plants display a suite of phenotypic traits defined as the shade avoidance syndrome (SAS). The SAS helps to position the photosynthesizing leaves in the higher zones of a canopy where light conditions are more favorable. In this review we will discuss the physiological control mechanisms through which the photosensory signals are transduced into the adaptive phenotypic responses that make up the SAS. Using this mechanistic knowledge as a starting point, we will discuss how the SAS functions in the context of the complex multi-facetted environments, which plants usually grow in.Key words: competition, shade avoidance, hormones, cell wall, adaptive plasticity, photoreceptor, light     

Consequences of near and far between-population crosses for offspring fitness in a rare herb

Crosses between plants from different populations may result in heterosis or outbreeding depression. However, despite its importance for conservation, little is known about the spatial scale over which these effects may arise. To investigate the consequences of between-population crosses at two distinct spatial scales, we conducted reciprocal crosses between four populations from two regions in the rare perennial herb Aster amellus . We assessed seed set and offspring fitness in a common garden experiment. Overall, between-population crosses within regions (10 km) resulted in 8% lower seed set than within-population crosses, while between-region crosses (70 km) resulted in 17% higher seed set than within-population crosses. Moreover, offspring from between-population crosses produced 18% more flower heads than offspring from within-population crosses. We conclude that hybridisation between A. amellus plants from different populations did not lead to immediate outbreeding depression and, thus, could represent a valid conservation option to increase genetic diversity. Moreover, our results suggest that the distance between populations affects the outputs of between-population crosses and therefore needs to be taken into account when promoting gene flow between populations.     

Homosexual incest avoidance among females in captive Japanese macaques

This paper reports a systematic pattern of homosexual incest avoidance among females in a captive group of Japanese macaques (Macaca fuscata) culled from the Arashiyama-West troop known for its high rates of female homosexuality. The study group included three matrilines and two generations. Between eight and 11 females were sexually active over four consecutive mating seasons, and all engaged in both heterosexual and homosexual activity. While all females performed homosexual acts with almost all possible non-kin partners, they systematically avoided homosexual interactions with their mother, daughters, and sisters. This pattern could not be explained either in terms of kin not being simultaneously in estrus, kin avoiding affiliative interactions in general, or non-kin utilizing the tension-reducing effect of estrus to affiliate exclusively with each other. In contrast to homosexual females, heterosexual pairs of relatives (brother-sister, mother-son) were sometimes incestuous. Assuming that female homosexuality expresses the reproductive strategy of females unconstrained by male influence, the present results point to the strong tendency of females to avoid incest and suggest that males are primarily responsible for the reported exceptions to incest avoidance.     

杂交产生的遗传危害--以植物为例

杂交是自然界的普遍现象,并在农林业生产中发挥着重要作用,但如不注意亦会带来遗传危害。当把两个遗传差异较大的物种（种群）混植在一起时,我们要考虑远交衰退的危害,即杂交破坏了亲代具有的共适应等位基因组合,导致杂交后代适应性的降低;当杂交发生在两亲本个体（或花粉）数量悬殊时,我们就要考虑遗传同化的危害,即小种群一方由于产生自己“纯”后代数量的减少而被前者“稀释”掉,导致小种群遗传特异性丧失或灭绝。另外,当杂交体具有杂种优势时,它可取代亲本,威胁到亲本的生存;如果有害物种（种群）由渐渗杂交获得某种优良性状（抗病、抗药、抗逆性等）时,可能失去控制,造成生态危害。针对杂交在这几个方面潜在的遗传危害,本文在濒危物种的迁地和就地保护、生态恢复中的种源选择等方面提出相应的建议和措施。     

Pollen source affects female reproductive success and early offspring traits in the rare endemic plant Polemonium vanbruntiae (Polemoniaceae)

Understanding the relative magnitudes of inbreeding and outbreeding depression in rare plant populations is increasingly important for effective management strategies. There may be positive and negative effects of crossing individuals in fragmented populations. Conservation strategies may include introducing new genetic material into rare plant populations, which may be beneficial or detrimental based on whether hybrid offspring are of increased or decreased quality. Thus, it is important to determine the effects of pollen source on offspring fitness in rare plants. We established pollen crosses (i.e. geitonogamous‐self, autonomous‐self, intrasite‐outcross, intersite‐outcross and open‐pollinated controls) to determine the effects of pollen source on fitness (seeds/fruit and seed mass) and early offspring traits (probability of germination, number of leaves, leaf area and seedling height) in the rare plant Polemonium vanbruntiae. Open‐pollinated, intrasite‐outcross and geitonogamous‐self treatments did not differ in fitness. However, plants receiving autonomous‐self pollen had the lowest fitness and the lowest probability of seed germination. Intersite‐outcross plants contained fewer seeds/fruit, but seeds germinated at higher frequencies and seedlings were more vigorous. We also detected heterosis at the seed germination stage. These data may imply that natural populations of P. vanbruntiae exhibit low genetic variation and little gene flow. Evidence suggests that deleterious alleles were not responsible for reduced germination; rather environmental factors, dichogamy, herkogamy and/or lack of competition among pollen grains may have caused low germinability in selfed offspring. Although self‐pollination may provide some reproductive assurance in P. vanbruntiae, the result is a reduction in germination and size‐related early traits for selfed offspring.