Patterns Of Morphological Differentiation Research Articles

Ontogenetic skull variation in a shovel-headed amphisbaenian species.

Leposternon microcephalum is a species belonging to the Amphisbaenia, a group of burrowing reptiles. Amphisbaenia present various morphological and physiological adaptations that allow them to penetrate the ground and live underground, through a system of galleries and permanent chambers that they build themselves. Among the morphological adaptations in this group, those of the skull stand out as it serves as the main excavation tool. Four basic skull shapes are recognized: rounded, keeled, shovel-shaped, and spade-shaped. The skull of L. microcephalum belongs to this last type, which is considered the most specialized. The species inhabits soils that are highly compacted and difficult to penetrate. Among the species of Leposternon present in South America, L. microcephalum has the widest distribution, being found in all Brazilian biomes and neighboring countries such as Bolivia, Argentina, Paraguay, and Uruguay. The analysis of the skull of this species was carried out using three-dimensional geometric morphometrics (3D-GMM), a technique that allows comparative analysis, through robust statistical methods, of shape and its variations, using Cartesian coordinate data from a configuration of homologous landmarks. The technique allows the size and shape components of a structure to be analyzed separately. From an ontogenetic point of view, this methodology had also been used to investigate variations in Cynisca leucura, a member of the Amphisbaenidae with a rounded head. Our hypothesis is that the patterns of morphological differentiation in the skull, mainly in the intermediate and occipital regions, are similar in different Amphisbaenia species. Therefore, the objective of this study was to analyze cranial morphological variations in an ontogenetic series of L. microcephalum using 3D-GMM. Computed Tomographic scans of 13 specimens were analyzed: juveniles (N = 8) and adults (N = 5), based on 20 landmarks that characterize the skull. Principal components and regression analyses between shape (dependent variable) and size (independent variable) showed a clear difference between the cranial morphological pattern of juvenile individuals and that of adults. For instance, young specimens tend to have a dorsoventrally tall neurocranium, with the tip of the snout more anteriorly oriented and its dorsal border subtly curved. Dorsally, the parietal region is thicker and smoothly dome-shaped in juveniles. As in C. leucura, the variation was strongly correlated with the size change from juvenile to adult, indicating a dominant role for ontogenetic allometry in determining skull shape.

The skull variation of the olive field mouse Abrothrix olivacea (Cricetidae: Abrotrichini) is localized and correlated to the ecogeographic features of its geographic distribution.

The relationship between phenotypic variation and landscape heterogeneity has been extensively studied to understand how the environment influences patterns of morphological variation and differentiation of populations. Several studies had partially addressed intraspecific variation in the sigmodontine rodent Abrothrix olivacea, focusing on the characterization of physiological aspects and cranial variation. However, these had been conducted based on geographically restricted populational samples, and in most cases, the aspects characterized were not explicitly contextualized with the environmental configurations in which the populations occurred. Here, the cranial variation of A. olivacea was characterized by recording twenty cranial measurements in 235 individuals from 64 localities in Argentina and Chile, which widely cover the geographic and environmental distribution of this species. The morphological variation was analyzed and ecogeographically contextualized using multivariate statistical analyses, which also included climatic and ecological variation at the localities where the individuals were sampled. Results indicate that the cranial variation of this species is mostly clustered in localized patterns associated to the types of environments, and that the levels of cranial differentiation are higher among the populations from arid and treeless zones. Additionally, the ecogeographical association of cranial size variation indicate that this species does not follow Bergmann's rule and that island populations exhibit larger cranial sizes compared to their continental counterparts distributed at the same latitudes. These results suggest that cranial differentiation among the populations of this species is not homogeneous throughout its geographic distribution, and that the patterns of morphological differentiation are also not completely consistent with the patterns of genetic structuring that have been described recently. Finally, the analyses performed to ponder morphological differentiation among populations suggest that the contribution of genetic drift in the formation of these patterns can be ruled out among Patagonian populations, and that the selective effect imposed by the environment could better explain them.

Integrative taxonomy and phylogeny of leafless Vanilla orchids from the South‐West Indian Ocean region reveal two new Malagasy species

AbstractThe leafless Vanilla species complex from the South‐West Indian Ocean (SWIO) region has long been a taxonomic challenge, due to limited patterns of morphological differentiation and an absence of variation within chloroplast sequences. This complex includes seven known morphospecies: V. madagascariensis, V. bosseri, V. decaryana, and V. perrieri endemic to Madagascar, V. humblotii presumed as endemic to the Comoros Archipelago, but also present in Madagascar, V. roscheri from the East African coast, and V. phalaenopsis endemic to Seychelles. A previous population genetic study using microsatellite markers allowed us to distinguish, in addition to the five recognized Malagasy taxa, two other genetic clusters present in the East of the island. An integrative taxonomy approach was therefore conducted by combining microsatellite and morphological data used in the previous study with new data sets, and by adding ITS sequencing data, to validate the taxonomic level of these Malagasy genetic clusters and unravel phylogenetic relationships between SWIO species. As a result, based on phylogenetic, genotypic and morphological evidence, nine species were discriminated in the SWIO region, including seven in Madagascar, with two new eastern species. The leafless Vanilla group originated and diversified in Madagascar, from an ancestor of African descent, with three subsequent independent colonization events from Madagascar to the other territories of SWIO within the two main lineages (white versus yellow flower species). The new Malagasy species, V. allorgeae Andriamihaja & Pailler sp. nov., and V. atsinananensis Andriamihaja & Pailler sp. nov., are described and a new identification key is proposed.

Patterns of morphological differentiation withinManacus manacus(Aves: Pipridae) in Colombia: revisiting hypotheses of isolation and secondary contact

AbstractDetermining the factors responsible for phenotypic variation within species is a fundamental task in evolutionary ecology. Isolation by distance, isolation by environment and clines along secondary contact zones between formerly isolated populations are common patterns of morphological variation. In this study, we evaluated whether patterns of morphological variation exhibit association with isolation by distance, isolation by environment or secondary contact in populations of Manacus manacus with contrasting plumage colour. We used field and museum measurements of five morphological characters from 311 individuals from 88 localities distributed across a highly heterogeneous environmental range within Colombia. Climatic variables explained a higher proportion of the variation than geographic distance among localities. We found differences in wing and culmen length between white and yellow phenotypes of M. manacus in Colombia. Overall morphology did not change in a clinal fashion in relation to the contact zone and the few traits that exhibit clinal variation suggest a distant locality for the contact zone, not in line with our expectations by secondary contact between differentiated populations, suggesting alternative mechanisms for differentiation between subspecies. Our results suggest that this species exhibits marked morphological variation associated with changes in temperature and precipitation. These associations are consistent throughout the geographic range analysed, leading us to postulate that dispersal and local adaptation jointly shape the distribution of phenotypic variation.

Effects of Sex and Breeding Status on Skull Morphology in Cooperatively Breeding Ansell’s Mole-Rats and an Appraisal of Sexual Dimorphism in the Bathyergidae

African mole-rats of the genus Fukomys (Northern common mole-rats) combine a monogamous mating system and pronounced sexual size dimorphism; a pattern highly untypical for mammals. At the same time, they live in cooperatively breeding groups composed of reproductive and non-reproductive members of both sexes. How and to which degree sex and breeding status influence morphofunctional characters in eusocial mole-rats is not well characterized but essential to come to a comprehensive understanding of their peculiar social system. Here, we explore patterns of morphological differentiation in skulls of Ansell’s mole-rats (Fukomys anselli) by means of multivariate analysis of linear skull measurements combined with a 2D shape analysis of cranium and mandible. Compared to females, males display larger skulls relative to body size and show an expansion of the facial portion of the cranium, while reproductive status did not have an effect on any of the traits studied. We also show that species of Fukomys mole-rats display a scaling of relative sexual body size dimorphism in compliance to Rensch’s rule, which is deemed indicative of intense male intrasexual competition. For the bathyergid family as a whole, results of scaling analyses were more ambiguous, but also indicative of Rensch’s rule conformity. In line with genetic field data, our results point to a greater role of male-male conflicts in Fukomys than is traditionally assumed and support the notion that reproductive status does not correlate with morphofunctional segregation in these unusual rodents.

Intra- and interspecific morphological variation in sympatric and allopatric populations of Mustela putorius and M. eversmanii (Carnivora: Mustelidae) and detection of potential hybrids

European mustelids include the European polecat, Mustela putorius, and the steppe polecat, M. eversmanii. Both occur sympatrically in the Pannonian Basin, where M. eversmanii hungarica represents the westernmost part of the latter species and they allegedly hybridize. We investigated the morphological relationships in sympatric and allopatric populations of these mustelids with representative sampling, taxonomic and geographic coverage. We evaluated inter- and intraspecific patterns of morphological differentiation of 20 cranial measurements and four external traits by distance-based morphometric approaches and multivariate analyses. Our results revealed a considerable heterogeneity in cranial morphology. The two species appeared to be clearly differentiated although sympatric populations were closer to each other and had a slight overlap in the morphometric space. Within M. eversmanii, the subspecies and the nominal taxon only partially overlapped, and M. eversmanii eversmanii was more distant from M. putorius than subspecies hungarica. Although morphometric analyses revealed several intermediate individuals in size in sympatric M. eversmanii and M. putorius populations, only a small fraction of such specimens showed conflict in discrete morphological characters with the diagnostic discriminant function. We interpret these results as an indication of ongoing hybridisation between sympatric populations, but the low number of hybrids identified suggests limited genetic exchange between the species.

Biome variation, not distance between populations, explains morphological variability in the orchid bee Eulaema nigrita (Hymenoptera, Apidae, Euglossini)

The sampling of orchid bees across different biomes provides an excellent opportunity to analyze morphological variability in this group. We examined the morphological variation of populations of Eulaema nigrita in the context of the determination of geographic origin. It also evaluated population variability of this group in different landscapes from two important biomes, Atlantic Forest, Brazilian Savanna, and the transition zone between them. These analyses were achieved by documenting the pattern of morphological differentiation using geometric morphometric analysis of the wings of 256 individuals, sampled from nine locations, from four different physiognomies. Results indicated that individuals from the Atlantic Forest physiognomies are larger than the ones from the Savanna. The clusterization of individuals was based on landscape features of the sampling areas. The results indicate little or even a complete absence of population structure. Overall, site-specific population differentiation is not strongly supported by wing traits, reinforcing the statement consistent with the broader pattern that orchid bees have a high migratory capacity. However, the subtle differentiation may indicate the existence of locally adapted traits kept by female philopatry or phenotypic plasticity triggered by environmental factors yet to be studied.

Morphometric analysis of the Habenaria parviflora complex (Orchidaceae)

We analyzed patterns of morphological differentiation of the Habenaria parviflora complex (Orchidaceae), through morphometric analyses of populations and morphotypes, aiming at evaluating current taxonomic proposals and at identifying discriminative characters for the delimitation of taxa. We performed multivariate and univariate morphometric analyses using 18 morphological characters of 675 individuals from 65 populations distributed throughout Brazil, Argentina and Uruguay, representing 12 morphotypes that comprise nearly all the morphological diversity and geographic distribution of the complex. The group presents morphological patterns difficult to understand which suggest that the complex does not correspond to a single species, nor does each morphotype correspond to a taxon. It was possible to clearly differentiate only two taxa, apart from H. parviflora, by a combination of characters: H. paulensis and H. ulei. Characters associated with flower size, leaf width and opening angle of the sepals were the most discriminatory for both species. The relationships between the populations of the remaining morphotypes exhibited high overlap in the analyses, making it impossible to define morphological groups with the characters used. The number of flowers, ovary length and angles between floral structures, not previously used in the taxonomy of this complex, are important characters for the recognition of taxa and can be further explored by future taxonomic studies of both the group and the genus.

Morphological variation of leaf traits in the Ternstroemia lineata species complex (Ericales: Penthaphylacaceae) in response to geographic and climatic variation.

Variation in leaf morphology is correlated with environmental variables, such as precipitation, temperature and soil composition. Several studies have pointed out that individual plasticity can largely explain the foliar phenotypic differences observed in populations due to climatic change and have suggested that the environment plays an important role in the evolution of plant species by selecting for phenotypic variation. Thus, the study of foliar morphology in plant populations can help us identify the environmental factors that have potentially influenced the process of species diversification. In this study, we analyzed morphological variation in the leaf traits of the Ternstroemia lineata species complex (Penthaphylacaceae) and its relation to climatic variables across the species distribution area to identify the patterns of morphological differentiation within this species complex. Based on the collected leaves of 270 individuals from 32 populations, we analyzed nine foliar traits using spatial interpolation models and multivariate statistics. A principal component analysis identified three main morphological traits (leaf length and two leaf shape variables) that were used to generate interpolated surface maps to detect discrete areas delimited by zones of rapid change in the values of the morphological traits. We identified a mosaic coarse-grain pattern of geographical distribution in the variation of foliar traits. According to the interpolation maps, we could define nine morphological groups and their geographic distributions. Longer leaves, spatulate leaves and the largest foliar area were located in sites with lower precipitation and higher seasonality of precipitation following a northwest–southeast direction and following significant latitudinal and longitudinal gradients. According to the phenogram of the relationships of the nine morphological groups based on morphological similarity, the putative species and subspecies of the T. lineata species complex did not show a clear pattern of differentiation. In this study, we found a complex pattern of differentiation with some isolated populations and some other contiguous populations differentiated by different traits. Further genetic and systematic studies are needed to clarify the evolutionary relationships in this species complex.

Exaggerated male forelegs are not more differentiated than wing morphology in two widespread sister species of black scavenger flies

Sexual selection represents a potent force that can drive rapid population differentiation in traits related to reproductive success. Hence, sexual traits are expected to show greater population divergence than non‐sexual traits. We test this prediction by exploring patterns of morphological differentiation of the exaggerated fore femur (a male‐specific sexual trait) and the wing (a non‐sexual trait) among allopatric and sympatric populations of the widespread sister dung fly species Sepsis neocynipsea and Sepsis cynipsea (Diptera: Sepsidae). While both species occur in Eurasia, S. neocynipsea also abounds in North America, albeit previous studies suggest strong differentiation in morphology, behavior, and mating systems. To evaluate the degree of differentiation expected under neutrality between S. cynipsea, European S. neocynipsea, and North American S. neocynipsea, we genotyped 30 populations at nine microsatellite markers, revealing almost equal differentiation between and minor differentiation among geographic populations within the three lineages. Landmark‐based analysis of 18 populations reared at constant 18 and 24°C in a laboratory common garden revealed moderate temperature‐dependent phenotypic plasticity and significant heritable differentiation in size and shape of male forelegs and wings among iso‐female lines of the three lineages. Following the biological species concept, there was weaker differentiation between cross‐continental populations of S. neocynipsea relative to S. cynipsea, and more fore femur differentiation between the two species in sympatry versus allopatry (presumably due to character displacement). Contrary to expectation, wing morphology showed as much shape differentiation between evolutionary independent lineages as fore femora, providing no evidence for faster diversification of traits primarily engaged in mating.

Multiple independent origins of intermediate species between Sorbus aucuparia and S. hybrida (Rosaceae) in the Baltic region

Populations intermediate between the diploid and sexual Sorbus aucuparia and the tetraploid and facultative apomictic Sorbus hybrida are scattered in coastal regions of southern Scandinavia. Our aims were to investigate whether these populations were of local and independent origins, whether they were morphologically and molecularly distinct from each other and whether they could give rise to constant offspring by apomixis. Six intermediate populations from the Baltic Sea basin were studied for variation at nuclear and plastid microsatellite loci, for morphological differentiation patterns, and for ploidy level by flow cytometry. Seeds were sown to check for constancy with the mother plants. Three populations from Gotland and possibly the small population from Uppland were in each case fixed for a unique combination of genetic markers, had restricted variation in leaf shape and were morphologically divergent from each other. Flow cytometry analysis showed that the four genetically monomorphic populations were consistently triploid. Cultivation showed that offspring from trees within two of the monomorphic populations had leaf shapes closely similar to the mother individuals. In contrast, a population from Gotland and a population from Åland were variable at molecular marker loci and were variable in leaf shape. The three monomorphic Gotland populations and possibly also the Uppland population propagate asexually by apomixis, and they have independent origins. The two variable populations are apparently composed of hybrids that have been formed repeatedly and independently between individuals of the two parental species growing at the same sites. One of the Gotland apomicts has already been described as Sorbus teodori. Sorbus faohraei Hedrén & J.Levin and Sorbus atrata Hedrén & J.Levin are described as new apomictic species from Gotland.

Phylogeographic analyses of the pampas cat (Leopardus colocola; Carnivora, Felidae) reveal a complex demographic history.

The pampas cat is a small felid that occurs in open habitats throughout much of South America. Previous studies have revealed intriguing patterns of morphological differentiation and genetic structure among its populations, as well as molecular evidence for hybridization with the closely related L. tigrinus. Here we report phylogeographic analyses encompassing most of its distribution (focusing particularly on Brazilian specimens, which had been poorly sampled in previous studies), using a novel dataset comprising 2,143 bp of the mitogenome, along with previously reported mtDNA sequences. Our data revealed strong population strutucture and supported a west-to-east colonization process in this species’ history. We detected two population expansion events, one older (ca. 200 thousand years ago [kya]) in western South America and another more recent (ca. 60-50 kya) in eastern areas, coinciding with the expansion of savanna environments in Brazil. Analyses including L. tigrinus individuals bearing introgressed mtDNA from L. colocola showed a complete lack of shared haplotypes between species, indicating that their hybridization was ancient. Finally, we observed a close relationship between Brazilian/Uruguayan L. colocola haplotypes and those sampled in L. tigrinus, indicating that their hybridization was likely related to the demographic expansion of L. colocola into eastern South America.

Morphological variability of <i>Tilapia zillii</i> (Gervais, 1848) from selected reservoirs in southwestern, Nigeria

Tilapia zillii is one of the dominant cichlids in southwestern reservoirs of Nigeria. Morphological variation was investigated among three populations (Opa, Ero and Asejire reservoirs) of this species using univariate and multivariate analysis. This was with a view to determining the pattern of morphological differentiation among them. Measurements of twenty five morphometric characters and six meristic counts were recorded on fifty specimens each. Univariate analysis of variance showed significant differences (p< 0.005) between the means of the three groups for 20 out of 25 morphometric measurements while there was no significant difference between the means of the three groups for most of the meristic characters. Canonical variate analysis results for the morphometric data shows overlap of clusters of fish specimens from Opa and Ero Reservoirs as well as Ero and Asejire Reservoirs. However, there was no overlap between T. zillii samples from Asejire and Ero Reservoir. Results established heterogeneity in morphology among populations of Tilapia zillii inhabiting the three reservoirs based on univariate and multivariate analysis of the morphometric characters only. The meristic characters could not delineate the three populations. The study therefore concluded that populations of T. zillii from Ero and Asejire reservoirs were phenotypically separable populations of the same species while those from Opa reservoir are somewhat morphologically related to both of them.Keywords: Meristics, Morphometrics, Phenotypically, Reservoir, Variation

Archipelagos of the Anthropocene: rapid and extensive differentiation of native terrestrial vertebrates in a single metropolis.

Some of the best evidence for rapid evolutionary change comes from studies of archipelagos and oceanic islands. City parks are analogous systems as they create geographically isolated green spaces that differ in size, structure and complexity. Very little, however, is known about whether city parks within a single urban centre drive selection and result in the diversification of native species. Here, we provide evidence for the rapid genetic and morphological differentiation of a native lizard (Intellagama lesueurii) at four geographically close yet unconnected parks within one city. Year of establishment of each city park varied from 1855 (oldest) to 2001 (youngest) equating to a generation time range of 32 to three generations. Genetic divergence among city park populations was large despite the small pairwise geographic distances (<5km) and found to be two to three times higher for microsatellites and three to 33 times higher for mtDNA relative to nonurban populations. Patterns of morphological differentiation were also found to be most extensive among the four city park populations. In contrast to nonurban populations, city park populations showed significant differentiation in relative body size, relative head and limb morphology and relative forelimb and hindlimb length. Crucially, we show that these patterns of differentiation are unlikely to have been caused by founder events and/or drift alone. Our results suggest that city park 'archipelagos' could represent theatres for rapid evolution that may, in time, favour adaptive diversification.

P3.03-016 Association between the Stainability of the Neurofibromatosis Type 2 Gene-Related Protein Merlin and the Tumor Properties of Mesotheliomas: Topic: Mesothelioma Transitional

Mutations in the genes cyclin-dependent kinase inhibitor 2A (CDKN2A), BRCA-1 associated protein 1 (BAP1), and neurofibromatosis type 2 (NF2) are observed in malignant pleural mesothelioma (MPM). We observed biallelic BAP1 alterations in 61% of MPMs and found that mutations are particularly frequent in epithelioid-type malignant mesotheliomas (Cancer Sci, 103:868-74, 2012). In addition, Loss-of-function mutations in NF2 are relatively frequent (40%) in MPMs have indicated. Merlin is a tumor suppressor protein coded by NF2; both merlin and the ezrin/radixin/moesin proteins are associated with suppression of invasion and metastasis of tumor cells. In this study, we examined the association between stainability of merlin and the tumor properties of MPM. Following definitive histological diagnoses of 35 cases of MPM (epithelial: n=31, biphasic: n=2, desmoplastic: n=2), we conducted immunohistochemical staining for merlin in thin sections of paraffin-embedded tumor tissue. Stainability was assessed with H-scores. The clinical stage of MPM was defined at the time near the tumor tissue harvesting time; the association between the clinical stage and therapeutic outcomes was assessed based on the outcomes of first-line chemotherapy with cisplatin (CDDP) or carboplatin(CBDCA) plus pemetrexed (PEM). The anti-merlin antibody used was LS-B394 (LSBio, Seattle, Washington, USA). 1) Seven MPMs (20%) were negative or weakly positive for merlin (H-score 0-30); of these seven MPMs, one was desmoplastic, while six were epithelial. Six MPMs were strongly positive for merlin (H-score ≥250); all six of these MPMs were epithelial. 2) No difference in merlin stainability was observed between epithelial (n=31) and non-epithelial (n=4) MPMs. Similarly, on examination of the association between stainability and IMIG staging, no differences in stainability were observed between stages 1 to 4. 3) No differences in stainability were observed between the first-line chemotherapy partial response group and progressive disease group. Loss-of-function mutations in the tumor suppressor gene NF2 lead to enhanced expression of focal adhesion kinase; although these mutations are demonstrated in decreased normal expression of the tumor suppressor protein merlin, no trend was observed in the morphological differentiation patterns of MPM. In addition, although the ratio of cells with high aldehyde dehydrogenase enzymatic activity is increased by CDDP/PEM treatment, we observed no association between CDDP/PEM sensitivity and merlin stainability. The association between NF2/merlin and tumor properties must be studied in more cases.

Phenotypic variation as an indicator of pesticide stress in gudgeon: Accounting for confounding factors in the wild

The response of organisms to environmental stress is currently used in the assessment of ecosystem health. Morphological changes integrate the multiple effects of one or several stress factors upon the development of the exposed organisms. In a natural environment, many factors determine the patterns of morphological differentiation between individuals. However, few studies have sought to distinguish and measure the independent effect of these factors (genetic diversity and structure, spatial structuring of populations, physical–chemical conditions, etc.).Here we investigated the relationship between pesticide levels measured at 11 sites sampled in rivers of the Garonne river basin (SW France) and morphological changes of a freshwater fish species, the gudgeon (Gobio gobio). Each individual sampled was genotyped using 8 microsatellite markers and their phenotype characterized via 17 morphological traits. Our analysis detected a link between population genetic structure (revealed by a Bayesian method) and morphometry (linear discriminant analysis) of the studied populations. We then developed an original method based on general linear models using distance matrices, an extension of the partial Mantel test beyond 3 matrices. This method was used to test the relationship between contamination (toxicity index) and morphometry (PST of morphometric traits), taking into account (1) genetic differentiation between populations (FST), (2) geographical distances between sites, (3) site catchment area, and (4) various physical–chemical parameters for each sampling site.Upon removal of confounding effects, 3 of the 17 morphological traits studied were significantly correlated with pesticide toxicity, suggesting a response of these traits to the anthropogenic stress. These results underline the importance of taking into account the different sources of phenotypic variability between organisms when identifying the stress factors involved. The separation and quantification of the independent effect of such factors provides an interesting outlook regarding the use of these evaluation metrics as indicators of ecosystem health.

Microevolutionary patterns in the common caiman predict macroevolutionary trends across extant crocodilians

Both extinct and extant crocodilians have repeatedly diversified in skull shape along a continuum, from narrow-snouted to broad-snouted phenotypes. These patterns occur with striking regularity, although it is currently unknown whether these trends also apply to microevolutionary divergence during population differentiation or the early stages of speciation. Assessing patterns of intraspecific variation within a single taxon can potentially provide insight into the processes of macroevolutionary differentiation. For example, high levels of intraspecific variation along a narrow-broad axis would be consistent with the view that cranial shapes can show predictable patterns of differentiation on relatively short timescales, and potentially scale up to explain broader macroevolutionary patterns. In the present study, we use geometric morphometric methods to characterize intraspecific cranial shape variation among groups within a single, widely distributed clade, Caiman crocodilus. We show that C. crocodilus skulls vary along a narrow/broad-snouted continuum, with different subspecies strongly clustered at distinct ends of the continuum. We quantitatively compare these microevolutionary trends with patterns of diversity at macroevolutionary scales (among all extant crocodilians). We find that morphological differences among the subspecies of C. crocodilus parallel the patterns of morphological differentiation across extant crocodilians, with the primary axes of morphological diversity being highly correlated across the two scales. We find intraspecific cranial shape variation within C. crocodilus to span variation characterized by more than half of living species. We show the main axis of intraspecific phenotypic variation to align with the principal direction of macroevolutionary diversification in crocodilian cranial shape, suggesting that mechanisms of microevolutionary divergence within species may also explain broader patterns of diversification at higher taxonomic levels.

Does predation drive morphological differentiation among Adriatic populations of the three-spined stickleback?

Morphometric differentiation among freshwater fish populations is a commonplace occurrence, although the underlying causes for this divergence often remain elusive. We analysed the degree and patterns of morphological differentiation among nine freshwater three-spined stickleback (Gasterosteus aculeatus) populations inhabiting isolated karst rivers of the Adriatic Sea basin, to characterise the phenotypic diversity and differentiation in these populations. The analyses revealed marked and significant morphometric differentiation – especially in traits related to predator defence amongst most populations – even among those located within close geographic proximity in the same catchment system. Accordingly, the degree of morphometric and neutral genetic differentiation, as assessed from variability in 15 microsatellite loci from a parallel study, were uncorrelated across the populations. However, PST/FST comparisons revealed that the degree of phenotypic differentiation (PST) among populations exceeded that to be expected from genetic drift alone, suggesting a possible adaptive basis for the observed differentiation. In fact, avian predation pressure and several physiochemical environmental variables were identified as the main putative drivers of the observed differentiation, particularly in the dorsal spines, ascending process and lateral plates. Hence, the high degree of morphometric differentiation among Adriatic three-spined stickleback populations appears to reflect adaptation to local ecological conditions.

Evidences of local adaptation in quantitative traits in Prosopis alba (Leguminosae).

Signals of selection on quantitative traits can be detected by the comparison between the genetic differentiation of molecular (neutral) markers and quantitative traits, by multivariate extensions of the same model and by the observation of the additive covariance among relatives. We studied, by three different tests, signals of occurrence of selection in Prosopis alba populations over 15 quantitative traits: three economically important life history traits: height, basal diameter and biomass, 11 leaf morphology traits that may be related with heat-tolerance and physiological responses and spine length that is very important from silvicultural purposes. We analyzed 172 G1-generation trees growing in a common garden belonging to 32 open pollinated families from eight sampling sites in Argentina. The multivariate phenotypes differ significantly among origins, and the highest differentiation corresponded to foliar traits. Molecular genetic markers (SSR) exhibited significant differentiation and allowed us to provide convincing evidence that natural selection is responsible for the patterns of morphological differentiation. The heterogeneous selection over phenotypic traits observed suggested different optima in each population and has important implications for gene resource management. The results suggest that the adaptive significance of traits should be considered together with population provenance in breeding program as a crucial point prior to any selecting program, especially in Prosopis where the first steps are under development.

Polymorphism in lake trout in Great Bear Lake: intra-lake morphological diversification at two spatial scales

Great Bear Lake is the most northerly lake of its size and provides unique opportunities for intraspecific diversification. Despite increasing attention to intraspecific polymorphism, several knowledge gaps remain (e.g. determining the extent of intraspecific diversification in large relatively pristine lakes and at which spatial scale it can occur). We focused on geographical patterns of morphological differentiation within lake trout (Salvelinus namaycush) to describe two levels of intralake diversification in Great Bear Lake. We used a combination of geometric and traditional linear measurements to quantify differences in body shape, head shape, and fin and body lengths among 910 adult lake trout from the five distinct arms of Great Bear Lake. Although head and fin linear measurements discriminated the three common morphotypes at the whole-lake level, inter-arm variation in body shape was observed within each morphotype. A comparison of genetic and morphological distance matrices revealed the lack of an association between the two sets of data, although both comparisons revealed an association in the inter-arm variation patterns among morphotypes, suggesting a phenotypically plastic response to distinct environments. The whole-lake and inter-arm morphological variation observed within lake trout demonstrates the importance of considering scale, especially across large lakes that exhibit marked complexity and a variety of freshwater habitats. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 114, 109–125.