RESUMO
Metopaulias depressus is a non-marine crab endemic to Jamaica that dwells in rainforest bromeliads and exhibits elaborate active parental care behavior. Current genomic resources on M. depressus are rare, limiting the understanding of its adaptation to terrestrial life in species that evolved from marine ancestors. This study reports the complete mitochondrial genome of M. depressus assembled using Sanger sequencing. The AT-rich mitochondrial genome of M. depressus is 15,765 bp in length and comprises 13 protein-coding genes (PCGs), 2 ribosomal RNA genes, and 22 transfer RNA genes. A single 691 bp-long intergenic space is assumed to be the control region (CR) or D-loop. A set of selective pressure analyses indicate that the entirety of the PCGs experience purifying selection. Cox1, cox2, nad5, cox3, and atp6 experience strong purifying selection, and atp8 experiences weak purifying selection compared to the rest of the PCGs. The secondary structures of most tRNA genes exhibit a standard 'cloverleaf' structure, with the exception of trnS1, which lacks the dihydroxyuridine (DHU) arm but not the loop, the trnH gene, which lacks the thymine pseudouracil cytosine (T) loop but not the arm, and trnM, which exhibits an overly developed T loop. A maximum likelihood phylogenetic analysis based on all PCGs indicated that M. depressus is more closely related to the genera Clistocoeloma, Nanosesarma, and Parasesarma than to Chiromantes, Geosesarma, and Orisarma. This study contributes to deciphering the phylogenetic relationships within the family Sesarmidae and represents a new genomic resource for this iconic crab species.
Assuntos
Braquiúros , Genoma Mitocondrial , Animais , Braquiúros/genética , Genoma Mitocondrial/genética , Genômica , Filogenia , RNA de Transferência/genéticaRESUMO
The genetic and morphometric population structures of the semiterrestrial crab Armases angustipes from along the Brazilian coast were examined. The influence of the Central South Equatorial Current on larval dispersal of A. angustipes also was evaluated. Six populations were sampled from estuarine areas in São Luis do Maranhão, Maranhão; Natal, Rio Grande do Norte; Maceió, Alagoas; Ilhéus, Bahia; Aracruz, Espírito Santo; and Guaratuba, Paraná. Patterns of genetic differentiation were assessed using DNA sequence data corresponding to parts of the mitochondrial cytochrome c oxidase subunit 1. Geometric morphometric techniques were used to evaluate morphological variation in shape and size of the carapace and right cheliped propodus. Our results revealed low genetic variability and lack of phylogeographic structure; geometric morphometrics showed statistically significant morphological differentiation and geographic structuring. Our data indicate the absence of possible barriers to gene flow for this mobile species, and no clear correlation of morphological or genetic variation with ocean currents and/or geographic distance. Our results also suggest that historical geological and climatological events and/or possible bottleneck effects influenced the current low genetic variability among the populations of A. angustipes.
Assuntos
Braquiúros/anatomia & histologia , Braquiúros/genética , Variação Genética , Animais , Braquiúros/classificação , Brasil , Complexo IV da Cadeia de Transporte de Elétrons/genética , Fluxo Gênico , Genética Populacional , Filogeografia , Dinâmica Populacional , Especificidade da Espécie , Movimentos da ÁguaRESUMO
BACKGROUND: During past glacial periods, many species of forest-dwelling animals experienced range contractions. In contrast, species living outside such moist habitats appear to have reacted to Quaternary changes in different ways. The Atlantic Forest represents an excellent opportunity to test phylogeographic hypotheses, because it has a wide range of vegetation types, including unforested habitats covered predominantly by herbaceous and shrubby plants, which are strongly influenced by the harsh environment with strong wind and high insolation. Here, we investigated the distribution of genetic diversity in the endemic sand dune ant Mycetophylax simplex across its known range along the Brazilian coast, with the aim of contributing to the understanding of alternative phylogeographic patterns. We used partial sequences of the mitochondrial gene cytochrome oxidase I and nuclear gene wingless from 108 specimens and 51 specimens, respectively, to assess the phylogeography and demographic history of this species. To achieve this we performed different methods of phylogenetic and standard population genetic analyses. RESULTS: The observed genetic diversity distribution and historical demographic profile suggests that the history of M. simplex does not match the scenario suggested for other Atlantic Forest species. Instead, it underwent demographic changes and range expansions during glacial periods. Our results show that M. simplex presents a shallow phylogeographic structure with isolation by distance among the studied populations, living in an almost panmictic population. Our coalescence approach indicates that the species maintained a stable population size until roughly 75,000 years ago, when it underwent a gradual demographic expansion that were coincident with the low sea-level during the Quaternary. Such demographic events were likely triggered by the expansion of the shorelines during the lowering of the sea level. CONCLUSIONS: Our data suggest that over evolutionary time M. simplex did not undergo dramatic range fragmentation, but rather it likely persisted in largely interconnected populations. Furthermore, we add an important framework about how both glacial and interglacial events could positively affect the distribution and diversification of species. The growing number of contrasting phylogeographic patterns within and among species and regions have shown that Quaternary events influenced the distribution of species in more ways than first supposed.
Assuntos
Formigas/genética , Filogeografia , Animais , Formigas/classificação , Formigas/enzimologia , Evolução Biológica , Brasil , Clima , DNA Mitocondrial/genética , Ecossistema , Complexo IV da Cadeia de Transporte de Elétrons/genética , Variação Genética , Proteínas de Insetos/genética , Dados de Sequência Molecular , Filogenia , Densidade Demográfica , Dinâmica Populacional , Proteína Wnt1/genéticaRESUMO
In an experimental study, we compared reproductive and developmental traits of endemic sesarmid crabs from Jamaica living in landlocked limnic or terrestrial habitats. Laboratory rearing and behavioral observations showed that the larval development of Sesarma windsor, Sesarma dolphinum (both from freshwater brooks), and Metopaulias depressus (the bromeliad crab) invariably consists of two nonfeeding zoeal stages and a facultatively lecithotrophic megalopa. In a quantitative study of life-history processes characterizing this developmental mode, we provide for S. windsor first data of biomass and elemental composition (dry mass, W; carbon, hydrogen, nitrogen, collectively, CHN) during development from the egg through successive larval stages. These data show that larval independence of food is based on an enhanced female energy allocation in reproduction, reflected in unusually large egg size (1.45-1.70 mm), as well as high contents of C and H (about 60% and 9%, respectively) and high C : N ratios (7.6-8.4) in eggs and early larvae. During zoeal development, about 6% of initial W and 9% of N but 13% each of C and H were lost; similar losses occurred during megalopal development in continued absence of food. These patterns reflect the metabolic utilization of stored organic matter, with preferential degradation of lipid reserves. Fed megalopae gained greater amounts of W and N as compared with C and H (increments of 37% and 38% vs. 25% and 19%, respectively), indicating preferential investment of nutritional energy in proteins required for the formation of new tissues and organs, while generally decreasing proportions of CHN within total W suggested an increasing mineralization of the exoskeleton. Although survival and molt cycle duration of the megalopa stage were not affected by absence of food, significant effects were found in the size of first-stage juvenile crabs, indicating a trade-off between nutritional flexibility in the last larval stage and postmetamorphic fitness. Similar patterns of development and biomass in M. depressus as well as preliminary data obtained for S. dolphinum and Sesarma fossarum suggest that reproductive and developmental traits may be similar in all endemic Jamaican sesarmids. These traits are interpreted as life-history adaptations to development in landlocked habitats, probably playing a key role during adaptive radiation.