Sympatric Distribution Research Articles

Phylogeography of surfclams, Spisula solidissima, in the western North Atlantic based on mitochondrial and nuclear DNA sequences

The Atlantic surfclam, Spisula solidissima (Dillwyn), is broadly distributed in sandy sediments of the western North Atlantic between the Gulf of St. Lawrence and the Gulf of Mexico. In the United States, a substantial commercial fishery between Long Island and Cape Hatteras harvests offshore populations of one subspecies, S. s. solidissima. A smaller coastal form, S. s. similis Say (also known as S. s. raveneli Conrad), has a partially sympatric geographic distribution, but differs in several life-history characteristics. DNA sequence variation in mitochondrial cytochrome oxidase I (COI) and in introns at two nuclear calmodulin loci was examined to measure genetic divergence between the two subspecies and to test for population structure among populations of S. s. solidissima. Surfclams were collected from seven localities between 1994 and 2001. Based on both mitochondrial and nuclear DNA variation, the two subspecies of S. solidissima are reciprocally monophyletic, with a net COI divergence of 13.9%, indicating long-term reproductive isolation. The only significant differentiation among populations of S. s. solidissima (based on an AMOVA analysis of COI sequences) was between the Gulf of St. Lawrence and more southerly populations. A long internal branch in the S. s. solidissima genealogy coupled with low haplotype diversity in the northern-most population suggests that populations north and south of Nova Scotia have been isolated from each other in the past, with gene exchange more recently. Populations of S. s. similis from Atlantic and Gulf of Mexico coasts had a net COI divergence of 9.2%. Thus, diversification of Spisula spp. clams in the western North Atlantic involved an early adaptive divergence between coastal and offshore forms, with later barriers to dispersal emerging in the offshore form from north to south and in the coastal form between Atlantic and Gulf of Mexico populations.

MITOCHONDRIAL DNA DIVERGENCE DOES NOT REFLECT MORPHOLOGICAL DIFFERENCE BETWEEN MYOTIS CALIFORNICUS AND MYOTIS CILIOLABRUM

The California myotis, Myotis californicus, and western small-footed myotis, Myotis ciliolabrum, are 2 morphologically similar bats which have had a complex taxonomic history due to intraspecific geographic variation across their sympatric distribution in western North America. Despite several published differences, field identification remains problematic in the southwestern United States. Mitochondrial cytochrome-b and control region fragments were amplified from tissue samples (n ¼ 20) from Texas, Oklahoma, New Mexico, Arizona, Utah, and California to examine species boundaries and phylogenetic relationships. DNA sequences (1,184 bp) were used in parsimony and maximum-likelihood analyses. To corroborate species identification, cranial measurements from all specimens included in the molecular analysis along with additional specimens were analyzed statistically using principal components analysis (PCA). Individuals were designated either as M. californicus or M. ciliolabrum. Molecular analysis placed M. leibii within clades containing both M. californicus and M. ciliolabrum. In addition, sequence divergence and phylogenetic results do not recover distinct lineages for each species (M. californicus and M. ciliolabrum) as recognized by morphology. Our results suggest that these species have recently diverged, or alternatively that they are 1 phenotypically variable species. Based on network estimation of cytochrome-b haplotypes, phylogeographic structure is minimally represented between haplotypes with an east-west separation in the southwestern United States.

Mechanisms maintaining sympatric distributions of two ladyfish (Elopidae: é) morphs in the Gulf of Mexico and western North Atlantic Ocean

Two morphs of ladyfish exist in the western North Atlantic and adjacent waters: Elops saurus, a high‐count morph (79‐87 myomeres or vertebrae) in the north, and Elops sp., a low‐count morph (73–78 myomeres or vertebrae) in the south. It has been proposed that these morphs are two allopatric species, but significant questions about their ecology remain. We examined 4,597 specimens and found that E. saurus was distributed principally in the western North Atlantic and Gulf of Mexico, whereas Elops sp. was distributed principally in the Caribbean Sea. Mixing of both morphs occurred along the east coast of the United States and the gulf coast of Mexico. Our results are consistent with the hypothesis that these meristic differences arise from latitudinal differences in temperature between spawning areas (i.e., Jordan󂀙s rule). Dispersal via the Gulf Stream System and associated mesoscale features appear sufficient to explain all areas of sympatric distribution. Elops larvae were found nearly year‐round in Florida estuaries, but E. saurus larvae were dominant in winter and spring collections, and Elops sp. larvae were dominant in summer and autumn. Thus, juvenile Elops sp. experience a shorter growing season and a different suite of estuarine conditions than juvenile E. saurus. The low initial abundance and high mortality of Elops sp. reduce the potential for interbreeding with E. saurus where they are sympatric. Such ecological data uphold the postulation that the two morphs are different species and support the existence of macroscale biotic connectivity between the Caribbean region and North America.

Correlation between distyly and ploidy level in Damnacanthus (Rubiaceae)

Somatic chromosomes were observed in 661 individuals of 14 taxa, nine species and five varieties, of Damnacanthus (Rubiaceae). Chromosome numbers are reported for the first time for 13 taxa. Diploid (2n = 22) and tetraploid (2n = 44) counts were obtained. Distyly is reported for the first time for four species, D. angustifolius, D. henryi, D. labordei, and D. officinarum. A strong correlation exists between chromosome number and occurrence of distyly. Regardless of taxa in Damnacanthus, distylous populations are diploid, and monomorphic populations are tetraploid. Flowers of the monomorphic populations observed have a long style and short stamens with few exceptions. Polyploidization may have caused the breakdown of distylous to monomorphic flowers. In D. indicus, leaves from the tetraploid populations tend to be larger than those from the diploid populations. Populations of tetraploid D. indicus were distributed in more northern areas than those of the diploid. Three types of sympatric distribution were found for the varieties of D. indicus in Japan: diploid and tetraploid, two diploids, and two tetraploids. Based on the present chromosome number study, the taxonomy of the varieties of D. indicus should be revised.

Comparison of the olfactory sensitivity of two sympatric steppe grasshopper species (Orthoptera: Acrididae) to plant volatile compounds.

Electroantennogram (EAG) responses of male and female Oedipodinae grasshoppers, Oedaleus decorus asiaticus B.-Bienko and Angaracris barabensis Pall to 37 plant volatile compounds were recorded. The two species have sympatric distribution and synchronous seasonal activity in Inner Mongolia Grasslands. They have different host plant preference with Oedaleus decorus asiaticus graminivorous and A. barabensis forbivorous. The EAG response profiles to 37 compounds of the two species and their both sexes were similar. Most of the green leaf volatiles elicited higher EAG responses in both species and sexes than terpenic compounds and some aromatic compounds. Strong EAG responses were elicited by 6-carbon alcohols (1-hexanol, Z-hexen-2-ol-1, E-2-hexen-1-ol, E-hexen-3-ol-1), aldehyde (E-2-hexen-1-al), ester (Z-hexen-3-yl acetate), and 7-carbon alcohols (1-heptanol) in both species and sexes. Monoterpenes with functional groups of alcohols and aldehydes were more stimulating than other monoterpenes tested. The sesquiterpenes tested elicited relatively low responses. Benzaldehyde elicited the highest responses for both species among aromatic components. Oedaleus decorus asiaticus showed higher EAG responses than A. barabensis to the green leaf volatiles, 1-decanol, 1-nonanol, 1-pentanol, hexanal, Z-hexen-3-yl acetate and to the sesquiterpenes (-)-trans-caryophyllene. Males have higher responses than females in Oedaleus decorus asiaticus. No sexual difference was observed in A. barabensis. Dose-dependent responses to six selected chemicals were observed from females. In both species, all the chemicals tested elicit EAG responses at concentration between 10(-3) mol/L and 10(-2) mol/L, except that the responses of A. barabensis to terpineol had a threshold concentration of 10(-2) mol/L benzaldehyde and 1-hexanol had the highest slopes in dose curves, while 1-octen-3-ol showed the smallest slope in responses to the six chemicals tested. Comparative studies on the responses of two antennal sections and the whole antenna to six selected chemicals were carried out using females of both species. A significant EAG response was only recorded from the distal part of the antenna and not from the proximal seven segments.

Habitat segregation between sympatric Tibetan argali Ovis ammon hodgsoni and blue sheep Pseudois nayaur in the Indian Trans‐Himalaya

AbstractTibetan argali Ovis ammon hodgsoni and blue sheep Pseudois nayaur have almost completely overlapping distributions encompassing most of the Tibetan plateau and its margins. Such a sympatric distribution of related species with similar ecological requirements implies that there is some degree of resource partitioning. This may be accomplished on the basis of habitat and/or diet separation. This study evaluated such ecological separation on the basis of physical habitat partitioning by these two sympatric ungulates in Hemis High Altitude National Park, Ladakh, India, in an area where the argali established a small new population in 1978. Such separation was tested for on the basis of expected difference between the species in their proximity to cliffs, associated with species‐specific anti‐predator behaviour. Tibetan argali selected habitats away from cliffs while blue sheep selected habitats close to cliffs. Blue sheep also selected steep slopes whereas argali selected gentle slopes. The two species did not differ in their use of habitats in terms of elevation. They did, however, differ in their use of plant communities; blue sheep selected sub‐shrub and grass‐dominated communities whilst argali selected forb‐dominated communities. We suggest that the two species coexist in this site as a result of the differential use of habitat associated with their species‐specific anti‐predator strategies.

Biogeographical History and Morphological Evolution of Two Closely Related Ostracod Species, Ishizakiella Ryukyuensis and I. Miurensis

Abstract Individuals of the brackish water ostracod species Ishizakiella ryukyuensis are found sympatrically with those of the closely related species I. miurensis at the Kii Peninsula, western Japan, and possess a projection on the male copulatory duct. By contrast, individuals of this species recovered from the Nansei Islands, southern Japan, do not have such a projection. Molecular phylogenetic trees based on mitochondrial COI sequences consistently indicated that the populations at the Nansei Islands formed a paraphyletic group outside of a cluster consisting of the population at the Kii Peninsula. Thus, the development of the projection in the male copulatory organ is considered as a derived character for the individuals at the Kii Peninsula, and this feature may have been brought about by the sympatric distribution and a process of character displacement.

Can transgenic rice cause ecological risks through transgene escape?*

Abstract Alien transgene escape from genetically engineered rice to non-transgenic varieties or close wild relatives (including weedy rice) may lead to unpredictable ecological risks. However, for transgene escape to occur three conditions need to be met: (i) spatially, transgenic rice and its non-transgenic counterparts or wild relatives should have sympatric distributions; (ii) temporally, the flowering time of transgenic rice and the non-transgenic varieties or wild relatives should overlap; and (iii) biologically, transgenic rice and its wild relative species should have such a sufficiently close relationship that their interspecific hybrids can have normal generative reproduction. This paper presents research data on the geographic distribution, flowering habits, interspecific hybridization, and gene flow of cultivated rice (Oryza sativa.) and its closely related wild relatives containing the AA genome. The objective is to estimate the possibility of transgene escape to non-transgenic rice varieties ...

Spatial and ecological isolation in cicadas: First data from Tibicina (Hemiptera: Cicadoidea) in France

The seven taxa of the cicada genus Tibicina (T.corsica corsica, T. corsica fairmairei, T. garricola, T. haematodes, T. nigronervosa, T. quadrisignata, T. tomentosa) which occur in continental France and Corsica were investigated. Extrinsic factors (geographical barriers) and factors intrinsic to the ecology of species were considered in an effort to understand the biogeography of Tibicina. Three patterns related to intrinsic factors were recognised: (1) pairs of taxa with sympatric distributions but with divergent habitat preferences; (2) pairs of taxa with sympatric distributions and similar habitat but with allochronic occurrence; (3) pairs of taxa with similar ecology but with allopatric distributions. When taxa were separated by their habitat, the height of vegetation appeared to be more important than the floristic composition of the habitat. These factors lead to the partitioning of resources in time and space. All taxa occur in secondary vegetations. Human agro-pastoral activity has probably influenced the dynamics of cicada populations and the maintenance of isolation between them.

Diferenciação morfológica das espécies de peixes-rei, Odontesthes Evermann & Kendall (Osteichthyes, Atherinopsidae) no extremo sul do Brasil: morfometria multivariada

The systematic relationships in the species of the genus Odontesthes Evermann & Kendall, 1906 were analysed by multivariate morphometry, using data adjusted for alometric size effects by orthogonal projections. The results are discussed in terms of morphological differentiation to each geographic units. It was concluded that seven species were identified in the southern Brazilian coast. Five of them inhabit freshwater environments, O. bonariensis (Valenciennes, 1835), O. humensis De Buen, 1953, O. retropinnis (De Buen, 1953), O. aff. perugiae Evermann & Kendall, 1906 and O. mirinensis Bemvenuti, 1995. The freshwater atherinids with the largest body size, O. retropinnis, O. bonariensis and O. humensis, can be distinguished by snout size, mouth position and number of gill rakers on the first branchial arch. The small size silversides, Odontesthes aff. perugiae and O. mirinensis, showed features of similar morphologic and sympatric distribution. The remaining species were represented by O. incisa (Jenyns, 1842), that occurred in coastal areas and O. argentinensis (Valenciennes, 1835) in brackish waters. In the last species, intraespecific morphological variation is attributed to phenotypic plasticity, resulted from environmental conditions found in that ecosystem.

Alps, genes, and chromosomes: their role in the formation of species in the Sorex araneus group (Mammalia, Insectivora), as inferred from two hybrid zones

During the Pleistocene glaciations, the Alps were an efficient barrier to gene flow between isolated populations, often leading to allopatric speciation. Afterwards, the Alps strongly influenced the post-glacial recolonization of Europe and represent a major suture zone between differentiated populations. Two hybrid zones in the Swiss and French Alps between genetically and chromosomally well-differentiated species—the Valais shrew, Sorex antinorii, and the common shrew, S. araneus—were studied karyotypically and by analyzing the distribution of seven microsatellite loci. In the center of the Haslital hybrid zone the two species coexist over a distance of 900 m. Hybrid karyotypes, among them the most complex known in Sorex, are rare. F-statistics based on microsatellite data revealed a strong heterozygote deficit only in the center of the zone, due to the sympatric distribution of the two species with little hybridization between them. Structuring within the species (both F_IS and F_ST) was low. An hierarchical analysis showed a high level of interspecific differentiation. Results were compared with those previously reported in another hybrid zone located at Les Houches in the French Alps. Genetic structuring within and between species was comparable in both hybrid zones, although chromosomal incompatibilities are more important in Haslital, where a linkage block of the race-specific chromosomes should additionally impede gene flow. Evidence for a more restricted gene flow in Haslital comes from the genetically intermediate hybrid karyotypes, whereas in Les Houches, hybrid karyotypes are genetically identical to individuals of the pure karyotypic races. Genic and chromosomal introgression was observed in Les Houches, but not in Haslital. The possible influence of a river, separating the two species at Les Houches, on gene flow is discussed.

Sympatric distribution of two cryptic bat species across Europe

The analysis of echolocation calls and mitochondrial DNA sequences recently revealed the existence of two cryptic bat species in Western Europe which were regarded as «Pipistrellus pipistrellus» for more than 200 years. We now present data on acoustic and genetic characters across Europe including a novel genetic marker from the nuclear genome. Intraspecific variation of end frequencies of echolocation calls did not differ between geographic regions and only a little overlap existed between the two species. Nuclear and mitochondrial DNA sequences for the two species were highly divergent. No evidence was found for additional cryptic species in this group. With the exception of Scandinavia, both species occur across the whole of Europe and largely overlap in their range. The distribution of the species using echolocation calls at higher frequencies extends further north and the same species is also more common in the south along the Mediterranean Sea.

Sympatric distribution of two cryptic bat species across Europe

The analysis of echolocation calls and mitochondrial DNA sequences recently revealed the existence of two cryptic bat species in Western Europe which were regarded as «Pipistrellus pipistrellus» for more than 200 years. We now present data on acoustic and genetic characters across Europe including a novel genetic marker from the nuclear genome. Intraspecific variation of end frequencies of echolocation calls did not differ between geographic regions and only a little overlap existed between the two species. Nuclear and mitochondrial DNA sequences for the two species were highly divergent. No evidence was found for additional cryptic species in this group. With the exception of Scandinavia, both species occur across the whole of Europe and largely overlap in their range. The distribution of the species using echolocation calls at higher frequencies extends further north and the same species is also more common in the south along the Mediterranean Sea.

A contribution to the knowledge of a Chinese endemic genus Stilpnodiscus Möllendorff, 1899 (Gastropoda: Pulmonata: Bradybaenidae), with a description of two new species

1. A taxonomic note on the helicoid land snail genus Traumatophora (Eupulmonata, Camaenidae) Min Wu ZooKeys CrossRef

Genetic relationships and variation in the tropical mimosoid legume Desmanthus assessed by random amplified polymorphic DNA

A number of Desmanthus spp. are being evaluated for forage potential on clay soils in the tropics and subtropics and three cultivars have already been released in Australia. These accessions have been chosen from the large number of Desmanthus accessions collected from the Americas over the last 40 years. The utilization of this genetic resource is dependent on understanding the diversity within and between species. Hence 284 accessions, representing 11 species, were analysed using RAPD markers. There was considerable polymorphism in D. virgatus, D. leptophyllus and D. pernambucanus but this was not always uniform across the geographical range of these species. There was little polymorphism in D. pubescens. Few accessions of D. acuminatus, D. paspalaceus and D. tatuhyensis were represented in the collection, but these species, which have an almost sympatric distribution in Paraguay/Uruguay/Argentina/Brazil, showed affinities to D. leptophyllus and to each other. D. pernambucanus was the only species with representatives from regions other than the Americas, suggesting that this species in particular has the capacity to colonize new regions. The analysis indicated that the non-American D. pernambucanus germplasm probably originated from Brazil.

GENETIC VARIATION AND SYSTEMATIC DIVERSITY IN THE GHOST SHRIMP GENUS LEPIDOPHTHALMUS (DECAPODA: THALASSINIDEA: CALLIANASSIDAE)

The resurrected genus Lepidophthalmus defines group of estuarine burrowing shrimp, western Atlantic members of which were until recently treated as single homogeneous species. Individu­ als from fourteen Gulf of Mexico, two Caribbean, and one eastern Pacific localities were assayed by allozyme electrophoresis of 19 presumptive loci. Results were evaluated by principal compo­ nents analysis of individual polymorphic allele data for definition of populations. Allozyme data were used to compare populations by F-statistics and measurement of pairwise genetic distances. Populations of Lepidophthalmus from within the Gulf of Mexico resolve into three distinct genetic lineages, pairwise genetic distances of which are comparable to congeneric species-level taxa in other invertebrate groups. The most widespread lineage defines L. louisianensis and consists of all samples from the northern through northwestern Gulf. This species is both geographically and allozymically separated from two other lineages {Lepidophthalmus sp. a and Lepidophthalmus sp. b) that occurred sympatrically in restricted area of the southwestern Gulf of Mexico, providing the first account of sympatric distribution in the genus. Taxonomic status for the southwestern Gulf lineages remains unresolved, but both are allozymically distinct from the Caribbean congeners, L. jamaicense and L. sinuensis, as well as the eastern Pacific species, L. nr. bocourti.

Intersectional gene flow between insular endemics ofIlex(Aquifoliaceae) on the Bonin Islands and the Ryukyu Islands

Hybridization and introgression play important roles in plant evolution, and their occurrence on the oceanic islands provides good examples of plant speciation and diversification. Restriction fragment length polymorphisms (RFLPs) and trnL (UAA) 3'exon-trnF (GAA) intergenic spacer (IGS) sequences of chloroplast DNA (cpDNA), and the sequences of internal transcribed spacer (ITS) of nuclear ribosomal DNA were examined to investigate the occurrence of gene transfer in Ilex species on the Bonin Islands and the Ryukyu Islands in Japan. A gene phylogeny for the plastid genome is in agreement with the morphologically based taxonomy, whereas the nuclear genome phylogeny clusters putatively unrelated endemics both on the Bonin and the Ryukyu Islands. Intersectional hybridization and nuclear gene flow were independently observed in insular endemics of Ilex on both sets of islands without evidence of plastid introgression. Gene flow observed in these island systems can be explained by ecological features of insular endemics, i.e., limits of distribution range or sympatric distribution in a small land area.

COMPARATIVE BIOLOGY OF TWO JAPANESE FRESHWATER CRABS GEOTHELPHUSA EXIGUA AND G. DEHAANI (DECAPODA, BRACHYURA, POTAMIDAE)

Abstract The Japanese freshwater crab Geothelphusa exigua Suzuki and Tsuda, 1994, is sympatric with Geothelphusa dehaani (White, 1874) in riverine habitats in Ohsumi Peninsula, Kagoshima Prefecture, southern Kyushu, Japan. We examined a number of biological characteristics of both crabs in two rivers in Ohsumi Peninsula to elucidate the factors maintaining their sympatric distribution. Results showed few biological differences between the two species, except for maximum body sizes and habitat preference. Geothelphusa exigua is smaller than G. dehaani in the maximum body size and lives mainly in water (aquatic), whereas G. dehaani may live both in water and on land (amphibious).

Chloroplast DNA and nuclear DNA variation in the sympatric alder species, Alnus cordata (Lois.) Duby and A. glutinosa (L.) Gaertn.

The European alder species, Alnus cordata and A. glutinosa have sympatric distributions on Corsica and southern Italy, where they often grow in mixed populations. An assessment was made of the levels of genetic variation in the chloroplast and nuclear genomes of individual trees from 22 alder populations from Corsica and Italy. The distribution of 10 chloroplast DNA polymorphisms generated by the PCR-RFLP method shows strong geographic structuring of cpDNA haplotypes. Conversely, variation in the nuclear genome, as determined by ISSR analysis, is strongly correlated to the taxonomic affinities of the individual trees analysed. Approximately 50% of ISSR variation (P=0.00, AMOVA) could be attributed to differences between species. Possible reasons for the incongruence between variation in the chloroplast and nuclear genomes are discussed.

Chloroplast DNA and nuclear DNA variation in the sympatric alder species, Alnus cordata (Lois.) Duby and A. glutinosa (L.) Gaertn.

The European alder species, Alnus cordata and A. glutinosa have sympatric distributions on Corsica and southern Italy, where they often grow in mixed populations. An assessment was made of the levels of genetic variation in the chloroplast and nuclear genomes of individual trees from 22 alder populations from Corsica and Italy. The distribution of 10 chloroplast DNA polymorphisms generated by the PCR-RFLP method shows strong geographic structuring of cpDNA haplotypes. Conversely, variation in the nuclear genome, as determined by ISSR analysis, is strongly correlated to the taxonomic affinities of the individual trees analysed. Approximately 50% of ISSR variation (P=0.00, AMOVA) could be attributed to differences between species. Possible reasons for the incongruence between variation in the chloroplast and nuclear genomes are discussed.