Sperm transfer through forced matings and its evolutionary implications in natural guppy (Poecilia reticulata ) populations

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High-predation habitats affect the social dynamics of collective exploration in a shoaling fish

Collective decisions play a major role in the benefits that animals gain from living in groups. Although the mechanisms of how groups collectively make decisions have been extensively researched, the response of within-group dynamics to ecological conditions is virtually unknown, despite adaptation to the environment being a cornerstone in biology. We investigate how within-group interactions during exploration of a novel environment are shaped by predation, a major influence on the behavior of prey species. We tested guppies (Poecilia reticulata) from rivers varying in predation risk under controlled laboratory conditions and find the first evidence of differences in group interactions between animals adapted to different levels of predation. Fish from high-predation habitats showed the strongest negative relationship between initiating movements and following others, which resulted in less variability in the total number of movements made between individuals. This relationship between initiating movements and following others was associated with differentiation into initiators and followers, which was only observed in fish from high-predation rivers. The differentiation occurred rapidly, as trials lasted 5 min, and was related to shoal cohesion, where more diverse groups from high-predation habitats were more cohesive. Our results show that even within a single species over a small geographical range, decision-making in a social context can vary with local ecological factors

Numerical abundance and biomass reveal different temporal trends of functional diversity change in tropical fish assemblages

Funding: Fisheries Society of the British Isles; European Research Council (Grant Number(s): ERC AdG BioTIME 250189); The Leverhulme Trust (Grant Number(s): RPG-2019-402).Understanding how the biodiversity of freshwater fish assemblages changes over time is an important challenge. Until recently most emphasis has been on taxonomic diversity but it is now clear that measures of functional diversity can shed new light on the mechanisms that underpin this temporal change. Fish biologists use different currencies, such as numerical abundance and biomass, to measure the abundance of fish species. However, because they are not necessarily equivalent, these alternative currencies have the potential to reveal different insights into trends of functional diversity in natural assemblages. Here we asked how conclusions about temporal trends in functional diversity are influenced by the way in which the abundance of species has been quantified. To do this we computed two informative metrics, for each currency, for 16 freshwater fish assemblages in Trinidad's Northern Range that had been surveyed repeatedly over five years. We found that numerical abundance and biomass uncover different directional trends in these assemblages for each facet of functional diversity, and as such inform hypotheses about the ways in which these systems are being restructured. On the basis of these results we concluded that a combined approach, in which both currencies are employed, contributes to our understanding of the ecological processes that are involved in biodiversity change in freshwater fish assemblages.Publisher PDFPeer reviewe

Experimental harvesting of fish populations drives genetically based shifts in body size and maturation

Size-selective harvesting in commercial fisheries can induce rapid changes in biological traits. While experimental and wild harvested populations often exhibit clear shifts in body size and maturation associated with fishing pressure, the relative contributions of genetic and environmental factors to these shifts remain uncertain and have been much debated. To date, observations of so-called fisheries-induced evolution (FIE) have been based solely on phenotypic measures, such as size data. Genetic data are hitherto lacking. Here, we quantify genetic versus environmental change in response to size-selective harvesting for small and large body size in guppies (Poecilia reticulata) across three generations of selection. We document for the first time significant changes at individual genetic loci, some of which have previously been associated with body size. In contrast, variation at neutral microsatellite markers was unaffected by selection, providing direct genetic evidence for rapid evolution induced by size-selective harvesting. These findings demonstrate FIE in an experimental system, with major implications for the sustainability of harvested populations, as well as impacts on size-structured communities and ecosystem processes. These findings highlight the need for scientists and managers to reconsider the capacity of harvested stocks to adapt to, and recover from, harvesting and predation. © 2013 The Ecological Society of America

Lenin on the Agrarian and Peasant Questions

Lenin attached great importance to the processes of agricultural and rural development. This is understandable in view of the fact that tsarist Russia where he prepared a socialist revolution had all the characteristics of an agrarian peasant country. Thus it was in Russia that many theories came into being which were contrary to the Marxist interpretations of historical evolution. Using the example of agriculture and peasantry, their authors tried to prove Marxist analysis wrong. They insisted that the special features of agriculture call for different laws of development (influence of natural factors, work with living matter, land as a special means of production, etc.). Thus defined, the agrarian question raised by bourgeois and revisionist economists did not exist for Lenin. For this sphere too is penetrated by capitalism, which leads to concentration, differentiation and social contrasts. One can only speak of different forms of its emergence in agriculture and industry, while the basic features remain the same. There are numerous works in which Lenin argued with the Populists and other champions of the agrarian question. The second group of questions which Lenin was concerned with derives from attempts to determine the attitude of the proletariat towards the peasants. Like Engels and Kautsky before him, he too was in favour of a firm alliance with small and medium farmers in the preparation for and realization of the revolution and, after its victory, for a gradual inclusion of the peasants in large-scale socialist agriculture on the principle of voluntary agreement and financial interest. The third group of questions studied by Lenin refers to the systems of co- -operation and association. In voluntary large-scale association of small producers Lenin saw the only way for agricultural development in the conditions of pettv ownership. But this involved an indispensable need for the development of industry which would provide agriculture with the necessary means

Possible glimpses into early speciation: the effect of ovarian fluid on sperm velocity accords with post-copulatory isolation between two guppy populations.

Identifying mechanisms of reproductive isolation is key to understanding speciation. Among the putative mechanisms underlying reproductive isolation, sperm-female interactions (postmating-prezygotic barriers) are arguably the hardest to identify, not least because these are likely to operate at the cellular or molecular level. Yet sperm-female interactions offer great potential to prevent the transfer of genetic information between different populations at the initial stages of speciation. Here we provide a preliminary test for the presence of a putative postmating-prezygotic barrier operating between three populations of Trinidadian guppies (Poecilia reticulata), an internally fertilizing fish that inhabits streams with different levels of connectivity across Trinidad. We experimentally evaluate the effect of female ovarian fluid on sperm velocity (a predictor of competitive fertilization success) according to whether males and females were from the same (native) or different (foreign) populations. Our results reveal the potential for ovarian fluid to act as a postmating-prezygotic barrier between two populations from different drainages, but also that the strength of this barrier is different among populations. This result may explain the previous finding that, in some populations, sperm from native males have precedence over foreign sperm, which could eventually lead to reproductive isolation between these populations. This article is protected by copyright. All rights reserved

Provenance and threat-sensitive predator avoidance patterns in wild-caught Trinidadian guppies

The antipredator behaviour of prey organisms is shaped by a series of threat-sensitive trade-offs between the benefits associated with successful predator avoidance and a suite of other fitness-related behaviours such as foraging, mating and territorial defence. Recent research has shown that the overall intensity of antipredator response and the pattern of threat-sensitive trade-offs are influenced by current conditions, including variability in predation risk over a period of days to weeks. Here, we tested the hypothesis that long-term predation pressure will likewise have shaped the nature of the threat-sensitive antipredator behaviour of wild-caught Trinidadian guppies (Poecilia reticulata). Female guppies were collected two populations that have evolved under high- and low-predation pressure, respectively, in the Aripo River, Northern Mountain Range, Trinidad. Under laboratory conditions, we exposed shoals of three guppies to varying concentrations of conspecific damage-released chemical alarm cues. Lower Aripo (high-predation) guppies exhibited the strongest antipredator response when exposed to the highest alarm cue concentration and a graded decline in response intensity with decreasing concentrations of alarm cue. Upper Aripo (low-predation) guppies, however, exhibited a nongraded (hypersensitive) response pattern. Our results suggest that long-term predation pressure shapes not only the overall intensity of antipredator responses of Trinidadian guppies, but also their threat-sensitive behavioural response patterns

How predation shapes the social interaction rules of shoaling fish

Predation is thought to shape the macroscopic properties of animal groups, making moving groups more cohesive and coordinated. Precisely how predation has shaped individuals' fine-scale social interactions in natural populations, however, is unknown. Using high-resolution tracking data of shoaling fish (Poecilia reticulata) from populations differing in natural predation pressure, we show how predation adapts individuals' social interaction rules. Fish originating from high predation environments formed larger, more cohesive, but not more polarized groups than fish from low predation environments. Using a new approach to detect the discrete points in time when individuals decide to update their movements based on the available social cues, we determine how these collective properties emerge from individuals' microscopic social interactions. We first confirm predictions that predation shapes the attraction–repulsion dynamic of these fish, reducing the critical distance at which neighbours move apart, or come back together. While we find strong evidence that fish align with their near neighbours, we do not find that predation shapes the strength or likelihood of these alignment tendencies. We also find that predation sharpens individuals' acceleration and deceleration responses, implying key perceptual and energetic differences associated with how individuals move in different predation regimes. Our results reveal how predation can shape the social interactions of individuals in groups, ultimately driving differences in groups' collective behaviour.</jats:p