Geometric morphometrics for the taxonomy of 11 species of Anopheles (Nyssorhynchus) mosquitoes

The subgenus Anopheles (Nyssorhynchus) (Diptera: Culicidae) includes the primary vectors of Plasmodium spp. in Colombia. Most adult females of this subgenus are difficult to identify in the field using the available keys. With the objective of further investigating the discriminatory power of modern morphometrics, both landmark‐based and outline‐based approaches were explored using the wing venation geometry of 11 Anopheles (Nyssorhynchus) species. Wing shape was able to separate the closest species of the subgenus. When the 11 species were analysed together, validated classification scores on average 5.3–8.6 times higher than those expected by chance were observed. These scores computed from the total sample of 11 species were not satisfactory for the recognition of Anopheles benarrochi B, Anopheles oswaldoi s.l. and Anopheles strodei. These sibling species were captured in sympatry. To improve the identification power of the morphometric tool, it was necessary to analyse these species separately from the remaining species. The best classification scores were obtained using a combination of 12 landmarks collected not only on the intersections of wing veins, but also on spots. An outline approach also gave excellent reclassification scores. Another pair of sibling species, collected in allopatry, Anopheles nuneztovari and Anopheles rangeli, also showed high classification scores.     

Interspecific comparison of growth and shape within Diapterus (Gerreidae: Perciformes) using geometric morphometrics

Morphometric analyses can generate useful information to solve taxonomic problems by direct comparison of each species representative’s shape or by analyzing its growth patterns. In this study, growth patterns and shape variation of the four fish species belonging to the genus Diapterus (Gerreidae) were analyzed using geometric morphometrics. We examined 287 specimens, D. auratus (n = 65), D. aureolus (n = 76), D. brevirostris (n = 87) and D. rhombeus (n = 59). For the exploration of growth trajectories of each species, the standard length was used as a size measurement, and the Procrustes distance as a morphological variation measurement. We also compared averages of the morphological change direction within each species through a pairwise comparison between vector angles. These analyses were also used to select those fishes whose increase in size did not lead to a significant change in Procrustes distance. Once this subsample was selected, the body shapes of the four species were compared using Canonical variate Analysis and Multivariate Analysis of Variance. Diapterus aureolus showed the most different morphological trajectory and the most divergent vector within the genus. An average of 93% of correct classification was estimated from Mahalanobis distances. The Canonical Variate Analysis generated three statistically significant canonical variates (p < 0.001) and indicated that D. auratus, D. brevirostris, and D. rhombeus presented a more related shape between them than D. aureolus, as indicated in previous studies. In this context, we considered the shape and growth of D. aureolus with regard to its congeners can be an important element for suggesting a taxonomic rearrangement. However, our interpretation should be supported by phylogenetic analysis. Based in our study, we suggest that trajectories analyses can be directly used in morphometric comparisons to detect those specimens affected by allometry.     

First record of Eucinostomus melanopterus,Bleeker 1863 (Perciformes,Gerreidae) from the Río de la Plata estuary

We established the presence of Eucinostomus at the Río de la Plata Estuary (36°17′74′′S–56°46′68′′W). The report is based on specimen of 191.6 mm. total length, captured in shallow, warm and brackish water with sandy bottom. This is southernmost record for the Southwest Atlantic Ocean, and appears related with an event of low discharge of the Río de la Plata.     

Population parameters of the Pacific flagfin mojarra Eucinostomus currani (Perciformes: Gerreidae) captured by shrimp trawling fishery in the Gulf of California

Shrimp trawling fishery in the Gulf of California captures a wide variety of non-target species of fish, crustaceans, and mollusks that are relatively unknown. The Pacific flagfin mojarra Eucinostomus currani is a frequently found species in these catches, nevertheless, nothing is currently known about its population dynamics. To contribute to the knowledge on this fish species, we studied the size structure, growth, mortality, and the recruitment pattern during the 2004-2005 seasons. A total of 6,078 mojarra were captured from 350 samples, with minimum and maximum lengths of 4.5 cm and a maximum of 21.0 cm. The average total length of the four major cohorts was 11.4, 13.7, 15.6 and 18.0 cm, corresponding to ages 0.9, 1.2, 1.6 and 2.2 years, respectively, being the most abundant the 1.2 year-old group. The instant growth coefficient indicated moderate growth rates (K(s) = 0.81/year, K(E) = 0.85/year), corresponding to individuals living between 3.5 to 3.7 years. The estimated asymptotic lengths was L (infinity) = 21.8 cm. In general, the population could be considered healthy: natural mortality (M = 1.53/year); total mortality (Z = 2.73/year); condition factor (K = 0.01072); fishery mortality (F = 1.2/year) and exploitation rate (E = 0.43/year). The maximum reproduction period almost coincided with the closed season for shrimp fishing (March to August), thus we concluded that survival of the species is ensured because reproduction is indirectly protected.     

A geometric morphometric approach for disparity of the sulcus acusticus of sagitta in species of Gerreidae (Teleostei: Perciformes)

This paper explores shape disparity in the sulcus acusticus of saccular otolith using geometric morphometric methods in selected Gerreidae species. First, multivariate linear regressions between size (CS-log-transformed) and shape were implemented to uncover allometry in the variation of the sulcus acusticus at three levels: intraspecific, intrageneric, and interspecific. Second, we assessed species disparity to investigate if differences in disparity are associated with three biologically contrasting ecological or historical processes within the family. Specifically, we asked: (1) How has disparity changed as a result of an ecological shift from marine to freshwater habitat? (2) How has disparity changed in genera with increasing taxonomic richness? and (3) How did a vicariant event across the Panama isthmus changed disparity in a pair of sister species? Our results indicate that the disparity of the sulcus acusticus shape of the single freshwater species (Eugerres mexicanus) is in the middle of the range of values of the 17 marine species compared. This suggests that the change to a freshwater environment did not influence the variability of the sulcus acusticus. In the taxonomic comparisons, as expected, disparity is lowest in the monotypic Deckertichthys, while it increases with species number in Diapterus. In the vicariant pair, the Pacific basin species (Diapterus brevirostris) has a disparity value almost twice the value than in the Atlantic taxon (D. rhombeus). It remains to be investigated if the same disparity patterns documented here are associated to marine-freshwater ecological shifts and vicariant events in other fish families.

     

Urohyal size versus body-length and weight relationships for thirteen mojarras species (Perciformes: Gerreidae) in Mexican waters

Given that it has been shown that urohyal bones can be used to identify gerreid fish to the species level, predictive regression equations between urohyal size and fish standard length and weight of thirteen species of Gerreidae living along the coasts of Mexico, were calculated. All regressions were statistically significant with coefficients of variation and coefficient of determination values around 0.90 in most of cases. These regression equations could provide a reliable tool in trophic ecology and other studies by estimating the original body size and weight of fish from measuring urohyal bone lengths. Information provide from the urohyal bone-fish length and weight relationships also facilitates the assessment of the potential role of gerreid fish found in the diet of piscivorous species from Mexican waters.     

Larval, pre-juvenile and juvenile development of Diapterus peruvianus (Perciformes: Gerreidae)

The development of Diapterus peruvianus (Sauvage 1879) is based on 60 larvae collected in superficial tows made in Bahía Concepción, and on 16 pre-juvenile and juvenile organisms collected in Bahía de La Paz, B. C. S., México, using a standard plankton net and a rectangular epibenthonic net, respectively. Larvae of D. peruvianus show three large blotches on the dorsum of the gut that can fuse together and give the appearance of one large continuous blotch. There are two to three pre-anal pigments and 16 post-anal pigments in the ventral midline; cephalic pigments are present from the postflexion stage, as well as a serrated preoperculum. The pre-juvenile and juvenile organisms are distinguished by their body depth, the anal-fin formula, the serrated pre-operculum and the base pigments in the dorsal and anal fins.     

Supporting the existence of two isolated evolutionary lineages of Gerres (Perciformes: Gerreidae) in America

For many years in America, many authors have considered that the Gerres genus contained a single species, the yellowfin mojarra Gerres cinereus (Walbaum, 1792); however, others have recognized two species in this genus in the Neotropics. In this study, specimens of G. cinereus (sensu lato) caught throughout its geographic range on both coasts of America were compared for the first time to analyse divergence among the sampled populations. A genetic analysis based on DNA sequences from three mitochondrial genes and one nuclear gene revealed a clear separation of two clades, one in the Pacific and one in the Atlantic. Geometric morphometric differences, based on body shape, sagittae otoliths and urohyal bone features, were significant between the two groups, including separation by an accurate classification a posteriori by a canonical variate analysis (CVA) > 82% in all data sets (overall mean >91%). Integration of the results of these approaches indicates that there is sufficient evidence to support species status for Gerres simillimus Regan, 1907, and it should be considered a valid species in the neotropical Pacific.     

Geometric morphometrics of mandibles for dietary differentiation of Bovidae (Mammalia: Artiodactyla)

The mammalian family Bovidae has been widely studied in ecomorphological research, with important applications to paleoecological and paleohabitat reconstructions. Most studies of bovid craniomandibular features in relation to diet have used linear measurements. In this study, we conduct landmark-based geometric-morphometric analyses to evaluate whether different dietary groups can be distinguished by mandibular morphology. Our analysis includes data for 100 species of extant bovids, covering all bovid tribes and 2 dietary classifications. For the first classification with 3 feeding categories, we found that browsers (including frugivores), mixed feeders, and grazers are moderately well separated using mandibular shape. A finer dietary classification (frugivore, browser, browser–grazer intermediate, generalist, variable grazer, and obligate grazer) proved to be more useful for differentiating dietary extremes (frugivores and obligate grazers) but performed equally or less well for other groups. Notably, frugivorous bovids, which belong in tribe Cephalophini, have a distinct mandibular shape that is readily distinguished from all other dietary groups, yielding a 100% correct classification rate from jackknife cross-validation. The main differences in mandibular shape found among dietary groups are related to the functional needs of species during forage prehension and mastication. Compared with browsers, both frugivores and grazers have mandibles that are adapted for higher biomechanical demand of chewing. Additionally, frugivore mandibles are adapted for selective cropping. Our results call for more work on the feeding ecology and functional morphology of frugivores and offer an approach for reconstructing the diet of extinct bovids.     

Six new and one previously described species of Pseudorhabdosynochus (Monogenoidea, Diplectanidae) infecting the gills of groupers (Perciformes, Serranidae) from the Pacific coasts of Mexico and Panama

Six new and 1 previously described species of Pseudorhabdosynochus (Diplectanidae) are described and/or reported from the gill lamellae of 5 serranid (Perciformes) fish species from the Pacific waters in Guerrero State of Mexico and Panama City, Panama. These species are Pseudorhabdosynochus guerreroensis n. sp. from the Pacific mutton hamlet Alphestes inmaculatus Breder (type host), rivulated mutton hamlet Alphestes multiguttatus (Günther), and spotted grouper Epinephelus analogus Gill from Mexico; Pseudorhabdosynochus urceolus n. sp. from the Pacific graysby Cephalopholis panamensis (Steindachner) from Taboga Island in Panama; Pseudorhabdosynochus spirani n. sp. from the starry grouper Epinephelus labriformis (Jenyns) from Mexico and the Perlas Archipelago and Taboga Island in Panama; Pseudorhabdosynochus fulgidus n. sp. from E. labriformis from Mexico and the Perlas Archipelago and Taboga Island (type locality) in Panama; Pseudorhabdosynochus tabogaensis n. sp. from E. labriformis from Mexico and the Perlas Archipelago and Taboga Island (type locality) in Panama; Pseudorhabdosynochus anulus n. sp. from E. labriformis from Mexico and Taboga Island (type locality) in Panama; and Pseudorhabdosynochus amplidiscatum (Bravo-Hollis, 1954) Kritsky and Beverley-Burton, 1986 from E. analogus and E. labriformis from Mexico and the Perlas Archipelago and Taboga Island in Panama. All new species are mainly distinguished from other species of the genus by the shape and size of the sclerotized vagina and haptoral structures. The present specimens of Alphestes, Cephalopholis, and Epinephelus spp. represent new host records and Panama represents a new geographic record for species of Pseudorhabdosynochus. The apparent common feature supporting a close similarity of these diplectanids is a single, secondary ejaculatory bulb with thickened wall.     

Genetic differentiation between two color morphs of Gerres erythrourus (Perciformes: Gerreidae) from the Indo-Pacific region

A portion of the mitochondrial 16S rRNA gene was compared between two color morphotypes of Gerres erythrourus, viz. “yellow type” and “white type,” obtained from Ryukyu Islands, Japan, and various areas of the Indo-Pacific, respectively. Phylogenetic analyses showed that the haplotypes of each color morph were reciprocally monophyletic, supported by high bootstrap values. The degree of sequence difference between the two color morphs was comparable to that existing between species of the same complex as well as other distinct gerreid species. The genetic results together with their geographic range indicated that the two color morphs represent two distinct species. Supplementary material to this paper is available in electronic format at http://dx.doi.org/10.1007/s10228-005-0324-0     

Geometric morphometrics, neural networks and diagnosis of sibling Taterillus species (Rodentia, Gerbillinae)

The lack of diagnostic traits in sibling species means that great quantities of biogeographical and ecological data held in museum collections cannot be utilized effectively, leading to underestimates of biodiversity. In this study we applied neural networks (NN) and canonical variates analyses (CVA) to landmark measurements on the skulls of the West African species Taterillus arenarius , T. petteri , T. gracilis and T. pygargus in an attempt to discriminate species previously identified unambiguously from their karyotypes. Among suggested differences, the relationship between inflation of the tympanic bullae and lower population density is discussed. Cross-validated classification rates did not exceed 73%. Two hypotheses are proposed to explain such high phenotypic similarity: morphological plasticity limited by environmental constraints and the possibility that speciation has been too recent to allow significant morphological divergence.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77 , 319−327.     

Geometric morphometrics of the forewing shape and size discriminate Plebeia species (Hymenoptera: Apidae) nesting in different substrates

Historically, studies evaluating morphological diversity in stingless bees (Hymenoptera, Apidae: Meliponini) by geometric morphometrics have been used to successfully discriminate taxa and/or populations. Moreover, the use of geometric morphometrics to evaluate phylogenetic morphological variation among stingless bee species has received less attention. Here, we used geometric morphometrics to assess taxonomic discrimination and putative phylogenetic signals for six diapausing stingless bee species (Plebeia) occurring in southern Brazil. In all, 12 landmarks were captured from forewings of P. droryana, P. saiqui, P. emerina, P. remota, P. nigriceps and P. wittmanni. Our data show that the centroid size of the forewings reliably discriminated, for example, between P. droryana and P. emerina from P. saiqui. Moreover, this trait does not have a significant phylogenetic signal. In turn, we found that the overall accuracy in discriminating between the six Plebeia species according to forewing shape was 84%, while the confusion matrix achieved 71%. Interestingly, our discriminant analysis separated Plebeia species nesting in tree cavities from those nesting under granitic rocks. The latter group has second cubital (landmarks = 5, 6, 7), first medial (landmarks = 2, 3, 8) and first submarginal cells (landmarks = 3, 4, 9, 10) that are larger than those of species nesting in trees. The forewing shape showed a strong phylogenetic signal, therefore suggesting that its variation may be due to an evolutionary history shared between Plebeia species studied here rather than to environmental features. This work sheds light on the value of forewing size and shape attributes in discriminating Plebeia species within same genus. We suggest that landmarks separating different taxonomic groups could be incorporated into dichotomous keys to help in identifying clades of complex resolution.