The pace-of-life syndrome (POLS) hypothesis integrates covariation of life-history traits along a fast-slow continuum and covariation of behavioural traits along a proactive-reactive personality continuum. Few studies have investigated these predicted life-history/personality associations among species and between sexes. Furthermore, whether and how contaminants interfere with POLS patterns remains unexplored. We tested for covariation patterns in life history and in behaviour, and for life-history/personality covariation among species, among individuals within species and between sexes. Moreover, we investigated whether pesticide exposure affects covariation between life history and behaviour and whether species and sexes with a faster POLS strategy have a higher sensitivity to pesticides. We reared larvae of four species of Ischnura damselflies in a common garden experiment with an insecticide treatment (chlorpyrifos absent/present) in the final instar. We measured four life-history traits (larval growth rate during the pesticide treatment, larval development time, adult mass and life span) and two behavioural traits (larval feeding activity and boldness, each before and after the pesticide treatment). At the individual level, life-history traits and behavioural traits aligned along a fast-slow and a proactive-reactive continuum, respectively. Species-specific differences in life history, with fast-lived species having a faster larval growth and development, a lower mass at emergence and a shorter life span, suggested that time constraints in the larval stage were predictably driving life-history evolution both in the larval stage and across metamorphosis in the adult stage. Across species, females were consistently more slow-lived than males, reflecting that a large body size and a long life span are generally more important for females. In contrast to the POLS hypothesis, there was only little evidence for the expected positive coupling between life-history pace and proactivity. Pesticide exposure decreased larval growth rate and affected life-history/personality covariation in the most fast-lived species. Our study supports the existence of life-history and behavioural continua with limited support for life-history/personality covariation. Variation in digestive physiology may explain this decoupling of life history and behaviour and provide valuable mechanistic insights to understand and predict the occurrence of life-history/personality covariation patterns.
Evolução e Ecologia de Calopterygidae (Zygoptera: Odonata): Conhecimento Atual e Perspectivas de Pesquisa RESUMO -Neste artigo revisamos estudos sobre evolução e ecologia da família Calopterygidae. Os adultos são reconhecidos pelas asas pigmentadas e comportamento territorial. Três gêneros têm sido bem estudados: Hetaerina, Calopteryx e Mnais. As larvas desenvolvem-se em ambientes aquáticos e a seleção opera principalmente nesse período, resultando em indivíduos de grande massa muscular. Os adultos levam alguns dias para se tornarem sexualmente maduros e durante esse período alimentam-se extensivamente acumulando as reservas de gordura que consumirão para voar e produzir ovos. Entretanto, gregarinas parasitas podem consumir essas reservas. Os machos utilizam duas estratégias de acasalamento que podem ser determinadas geneticamente (Mnais) ou ambientalmente (Calopteryx e Hetaerina): territorialidade e não-territorialidade. No gênero Mnais as estratégias comportamentais parecem ser balanceadas de acordo com sua adaptabilidade ao longo do tempo. Os machos deCalopteryx, Mnais e Phaon realizam corte pré-cópula, comportamento ausente em Hetaerina. A pigmentação das asas dos machos parece sinalizar às fêmeas, durante a corte, algum nível de resistência imunológica a parasitas. Durante a cópula os machos retiram o esperma armazenado em cópulas anteriores pelas fêmeas. Há grande variação na habilidade e nos tipos de mecanismos para a retirada do esperma, assim como na morfologia genital de ambos sexos. Tal variação pode resultar de co-evolução entre os sexos direcionada a controlar o esperma armazenado. Após a cópula os machos defendem as fêmeas evitando que elas copulem com outros machos. Nessa revisão sugerimos aspectos a serem estudados nessa família. PALAVRAS-CHAVE: Reserva de gordura, pigmentação alar, capacidade imune, coevolução de genitália ABSTRACT -We review the studies of evolution and ecology in the Calopterygidae. Adults are easily distinguished for their pigmented wings and territorial behaviour. Three genera have been well studied: Hetaerina, Calopteryx and Mnais. Larvae develop in riverine aquatic environments. Selection operates at this stage to produce large muscle mass for adults. The adult spends some days until sexually ready. During this time, it feeds extensively to produce muscle fat for egg production and fl ight. However, gregarine parasites may ingest the fat reserves. Males may use two mating tactics or strategies that may be genetically (Mnais) or environmentally (Calopteryx andHetaerina) determined: territoriality and nonterritoriality. In Mnais, these strategies appear balanced in fi tness terms. Males of Calopteryx, Mnais and Phaon show a precopulatory courtship that is not the case for Hetaerina. Male wing pigmentation seems to signal how good the male is to deal immunologically with parasites to females during the male courtship. During copulation, males displace the sperm the female has stored in the storage organs from previous matings. There is an enormous variation in male sperm disp...
BackgroundStudying contemporary hybridization increases our understanding of introgression, adaptation and, ultimately, speciation. The sister species Ischnura elegans and I. graellsii (Odonata: Coenagrionidae) are ecologically, morphologically and genetically similar and hybridize. Recently, I. elegans has colonized northern Spain, creating a broad sympatric region with I. graellsii. Here, we review the distribution of both species in Iberia and evaluate the degree of introgression of I. graellsii into I. elegans using six microsatellite markers (442 individuals from 26 populations) and five mitochondrial genes in sympatric and allopatric localities. Furthermore, we quantify the effect of hybridization on the frequencies of the genetically controlled colour polymorphism in females of both species.ResultsIn a principal component analysis of the microsatellite data, the first two principal components summarised almost half (41%) of the total genetic variation. The first axis revealed a clear separation of I. graellsii and I. elegans populations, while the second axis separated I. elegans populations. Admixture analyses showed extensive hybridization and introgression in I. elegans populations, consistent with I. elegans backcrosses and occasional F1-hybrids, suggesting hybridization is on-going. More specifically, approximately 58% of the 166 Spanish I. elegans individuals were assigned to the I. elegans backcross category, whereas not a single of those individuals was assigned to the backcross with I. graellsii. The mitochondrial genes held little genetic variation, and the most common haplotype was shared by the two species.ConclusionsThe results suggest rapid species turnover in sympatric regions in favour of I. elegans, corroborating previous findings that I. graellsii suffers a mating disadvantage in sympatry with I. elegans. Examination of morph frequency dynamics indicates that hybridization is likely to have important implications for the maintenance of multiple female morphs, in particular during the initial period of hybridization.
Reproductive isolation is the defining characteristic of a biological species, and a common, but often untested prediction is a positive correlation between reproductive isolation and genetic divergence. Here, we test for this correlation in odonates, an order characterized by strong sexual selection. First, we measure reproductive isolation and genetic divergence in eight damselfly genera (30 species pairs) and test for a positive correlation. Second, we estimate the genetic threshold preventing hybrid formation and empirically test this threshold using wild populations of species within the Ischnura genus. Our results indicate a positive and strong correlation between reproductive isolation and genetic distance using both mitochondrial and nuclear genes cytochrome oxidase II (COII: r = 0.781 and 18S-28S: r = 0.658). Hybridization thresholds range from À0.43 to 1.78% for COII and À0.052-0.71% for 18S-28S, and both F 1 -hybrids and backcrosses were detected in wild populations of two pairs of Ischnura species with overlapping thresholds. Our study suggests that threshold values are suitable to identify species prone to hybridization and that positive isolation-divergence relationships are taxonomically widespread.
Continental islands offer an excellent opportunity to investigate adaptive processes and to time microevolutionary changes that precede macroevolutionary events. We performed a population genetic study of the fire salamander (Salamandra salamandra), a species that displays unique intraspecific diversity of reproductive strategies, to address the microevolutionary processes leading to phenotypic and genetic differentiation of island, coastal and interior populations. We used eight microsatellite markers to estimate genetic diversity, population structure and demographic parameters in viviparous insular populations and ovoviviparous coastal and interior populations. Our results show considerable genetic differentiation (F ST range: 0.06-0.27), and no clear signs of gene flow among populations, except between the large and admixed interior populations. We find no support for island colonization by rafting or intentional/accidental anthropogenic introductions, indicating that rising sea levels were responsible for isolation of the island populations approximately 9000 years ago. Our study provides evidence of rapid genetic differentiation between island and coastal populations, and rapid evolution of viviparity driven by climatic selective pressures on island populations, geographic isolation with genetic drift, or a combination of these factors. Studies of these viviparous island populations in early stages of divergence help us better understand the microevolutionary processes involved in rapid phenotypic shifts.
Population ecologists track wild animals over their lifetimes using mark-recapture methods. Odonates are easily marked and remain near water bodies, allowing for high recapture rates. In recent years, the focus in mark-recapture models has switched from population size estimates to survival and recapture rate estimation, and from testing hypotheses to model selection and inference. This chapter presents a review of the literature on mark-recapture studies, with a suggestion of areas where more research is needed. These include the effect of marking on survival and recapture rates, differences in survival between sexes and female colour morphs, the relative importance of processes in the larval and the adult stage in driving population dynamics, and the contribution of local and regional processes in shaping metapopulation dynamics.
Identifying environmental factors that structure intraspecific genetic diversity is of interest for both habitat preservation and biodiversity conservation. Recent advances in statistical and geographical genetics make it possible to investigate how environmental factors affect geographic organisation and population structure of molecular genetic diversity within species. Here we present a study on a common and wide ranging insect, the blue tailed damselfly Ischnuraelegans, which has been the target of many ecological and evolutionary studies. We addressed the following questions: (i) Is the population structure affected by longitudinal or latitudinal gradients?; (ii) Do geographic boundaries limit gene flow?; (iii) Does geographic distance affect connectivity and is there a signature of past bottlenecks?; (iv) Is there evidence of a recent range expansion and (vi) what is the effect of geography and climatic factors on population structure? We found low to moderate genetic sub-structuring between populations (mean FST = 0.06, Dest = 0.12), and an effect of longitude, but not latitude, on genetic diversity. No significant effects of geographic boundaries (e.g. water bodies) were found. FST-and Dest-values increased with geographic distance; however, there was no evidence for recent bottlenecks. Finally, we did not detect any molecular signatures of range expansions or an effect of geographic suitability, although local precipitation had a strong effect on genetic differentiation. The population structure of this small insect has probably been shaped by ecological factors that are correlated with longitudinal gradients, geographic distances, and local precipitation. The relatively weak global population structure and high degree of genetic variation within populations suggest that I. elegans has high dispersal ability, which is consistent with this species being an effective and early coloniser of new habitats.
Disentangling the relative importance and potential interactions of selection and genetic drift in driving phenotypic divergence of species is a classical research topic in population genetics and evolutionary biology. Here, we evaluate the role of stochastic and selective forces on population divergence of a colour polymorphism in seven damselfly species of the genus Ischnura, with a particular focus on I. elegans and I. graellsii. Colour-morph frequencies in Spanish I. elegans populations varied greatly, even at a local scale, whereas more similar frequencies were found among populations in eastern Europe. In contrast, I. graellsii and the other five Ischnura species showed little variation in colour-morph frequencies between populations. F ST -outlier analyses revealed that the colour locus deviated strongly from neutral expectations in Spanish populations of I. elegans, contrasting the pattern found in eastern European populations, and in I. graellsii, where no such discrepancy between morph divergence and neutral divergence could be detected. This suggests that divergent selection has been operating on the colour locus in Spanish populations of I. elegans, whereas processes such as genetic drift, possibly in combination with other forms of selection (such as negative frequency-dependent selection), appear to have been present in other regions, such as eastern Europe. Overall, the results indicate that both selective and stochastic processes operate on these colour polymorphisms, and suggest that the relative importance of factors varies between geographical regions.
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