Sympatric Occurrence Research Articles

Sympatric occurrence of two varieties of Corylopsis glabrescens in the Kisogawa basin, central Japan

Sympatric occurrence of two varieties of Corylopsis glabrescens in the Kisogawa basin, central Japan

Sympatric Occurrence of Eubranchiopoda in Ephemeral Pools: A Comment

Sympatric Occurrence of Eubranchiopoda in Ephemeral Pools: A Comment

Cyclops Kikuchii Smirnov, 1932 (Copepoda, Cyclopoida), Eine Selbständige Art Aus Süddeutschen Gewässern

The hitherto existing subspecies Cyclops vicinus kikuchii Smirnov, 1932 was originally described by materials from Japan; later it was found in Russia, Poland, and Czechoslovakia. Compared with Cyclops vicinus Uljanin, 1875 the subspecies is characterized mainly by the short inner furcal seta (no. 1) in proportion to furcal and body length. According to Wierzbicka (1934) both types could interbreed to produce fertile offspring. Materials collected in an old reservoir, the Neuweiher near Meersburg (Lake Constance), and further in Lake Seeg and in the Schwaltenweiher (southern Bavaria), allowed morphological and morphometrical studies (fig. 1, tab. I), completed by comparative chromatin diminution and enzyme electrophoresis. The morphological studies (tab. I) confirmed the differences in length of the inner furcal seta compared with C. vicinus. The only five specimens from Lake Seeg at least indicate the probability of a seasonal variation. The course of chromatin diminution (fig. 2) appears identical in qualitative aspects for both cyclopids. In the enzyme electrophoresis remarkable differences were found in GOT (glutamate oxaloacetate transferase), APK (arginine phosphokinase) and PGM (phosphoglucomutase) (fig. 3). Together with the morphological details and the sympatric occurrence with C. vicinus in Lake Seeg and in the Schwaltenweiher, these results confirm the separate status of the species Cyclops kikuchii Smirnov, 1932. This species passes its diapause during summer in the fifth copepodid instar, while C. vicinus aestivates in the fourth instar.

The Sympatric Occurrence of the Carapid Fishes Pyramodon ventralis and P. lindas in Japanese Waters

The Sympatric Occurrence of the Carapid Fishes Pyramodon ventralis and P. lindas in Japanese Waters

Bimodal echolocation in pipistrelle bats: are cryptic species present?

The pipistrelle bat Pipistrellus pipistrellus is the most widespread in Europe, and is often the most abundant bat species in northern and central Europe. P. pipistrellus has traditionally been considered as one species throughout Europe. Here we show that: (i) the echolocation calls of pipistrelles fall into two distinct frequency bands in Britain, with frequencies containing most energy averaging 46 kHz and 55 kHz; (ii) roosts consist of bats which use only one form of echolocation; (iii) small but significant differences in average gross morphology exist between the phonic types; and (iv) the two phonic types occur in sympatry over much of Britain. Recordings made from European populations show that bimodal echolocation is also typical of continental pipistrelles, with only one phonic type found in some areas, two types in sympatry in others. The sympatric occurrence of two phonic types, the lack of mixing of types between colonies, and the morphological divergence between phonic types suggests that P. pipistrellus may actually consist of at least two cryptic sibling species. The evolution of bimodal echolocation in bats is discussed, and a model involving disruptive selection is presented to show how sympatric speciation may occur.

A Morphometric Comparison of the Masked Shrew (Sorex cinereus) and Hayden's Shrew (Sorex haydeni) in Montana and Bordering States

A morphometric analysis of populations of Sorex cinereus and Sorex haydeni in Montana and neighboring states supports the species level distinction proposed in 1980. A comparison with populations in the Prairie Provinces of Canada suggests the presence of a clinal gradient of decreasing size from north to south for Sorex cinereus, while none was apparent for Sorex haydeni. The masked shrew (Sorex cinereus) is the most common and widely distributed shrew in North America. Its range encompasses virtually all of Canada and Alaska, the North- east, Upper Midwest, and northern Great Plains states, with extensions southward in the Appalachians and Rocky Mountains (Junge and Hoffmann 1981). The variability in the cranial characteristics of this species over its range was noted as early as 1928 (Jackson 1928). Van Zyll de Jong (1980) recently studied two subspecies of Sorex cinereus, S. c. cinereus and S. c. haydeni, in the Prairie Provinces of Canada. In considering morphological and ecological factors, and the sympatric occurrence of the two morphs and their apparent reproductive isolation in the northern part of their range, he concluded that these taxa were distinct species. Based upon his findings S. c. haydeni has since been elevated to species rank. As part of a tong-term study on the soricids of Montana we collected S. cinereus along its western Rocky Mountain range. It is the intent of the present mor- phometric study to clarify further the taxonomic status of the two taxa. This work is based upon craniometric comparisons of S. cinereus, and S. haydeni from Montana and adjacent states, and data reported by van Zyll de Jong (1980) for samples of these taxa from Canada.

Sympatric Occurrence of Three Species of Eubranchiopoda in a Vernal Prairie Pond in Southeastern Wyoming

Sympatric Occurrence of Three Species of Eubranchiopoda in a Vernal Prairie Pond in Southeastern Wyoming

Immigration and settlement pattern of Paralichthys dentatus and P. lethostigma in an estuarine nursery ground, North Carolina, U.S.A.

Immigration and settlement pattern of 0-group summer flounder ( Paralichthys dentatus) and southern flounder ( P. lethostigma) in an estuarine nursery are described. Flounders entering the estuary were transforming larvae. Despite their sympatric occurrence during larval immigration, the two species were found concentrated in different habitats. Sampling along transects within the estuary indicated that newly settled southern flounder were concentrated on tidal flats towards the head of the estuary while greatest numbers of summer flounder were captured on tidal flats in the middle reach of the system. Logistic regression analysis of presence/absence data indicated that salinity affected the distribution of southern flounder while substrate type was an important factor affecting the distribution of summer flounder. Numbers of both species on tidal flats declined in the spring, southern flounder appeared to move upstream to oligohaline riverine habitat and summer flounder appeared to move to high salinity salt marsh habitat. The segregated distribution apparent in juveniles is largely established during the immigration period. Differences in settling behaviour and subsequent movement and/or differential mortality occurring during settlement, appear important in determining the observed distribution of juvenile summer and southern flounder.

<i>Chironomus fraternus</i> sp. n. and <i>C. beljaninae</i> sp. n., sympatric sister species of the <i>aberratus</i> group in Fennoscandian reservoirs

The karyotypes, larvae, pupae and adults of Chironomus fraternus sp. n. and C. beljaninae sp. n. are described. The chromosomes of the two species have almost identical banding pattems; the polymorphisms in at least five of the seven chromosome arms are also the same. However, the chromosome number is 2n=8 in C . fraternus (AB, CD, EF, G), and 2n=6 in C. beljaninae (GAB, CD, EF). No hybrid individuals between the two species have been found as yet. Only slight diagnostic differences could be shown between the adults, pupae and larvae of the two species. The sympatric occurrence of C. fraternus and C. beljaninae in lakes of central Finland and Sweden points to speciation due to chromosome fusion. The species are closely related to C. aberratus, C. sororius and C. jonmartini; the five species may therefore be regarded as forming the "aberratus group" of the thummi complex of Chironomus.

Ökologische Prüfung von Morphospecies der „Tullbergia krausbaueri‐Gruppe”︁ (Insecta: Collembola)

Ecological Examination of the “Tullbergia krausbaueri” Morphospecies Group (Insecta: Collembola)Up to 1960 “Tullbergia krausbaueri (BÖRNER, 1901)” was understood to be only one good species. At present, this complex comprehends 8 genera with alltogether 43 species within the palearctic region, most being parthenogenetic. Ecological examinations of some of these morphospecies were made with regard to sympatric occurrence, soil layer preference, reactions on disturbances of soil ecosystems and stability of populations in time. The results confirm the morphologically defined species to be true biospecies.

Population‐genetic evidence for two species in Anopheles minimus in Thailand

Sympatric occurrence of homozygotes for two electromorphs controlled by a locus for octanol dehydrogenase, and the absence of heterozygotes, at two localities, indicates two isomorphic species within the taxon Anopheles minimus Theobald in Thailand. This view is supported by significant, relative deficiencies of heterozygotes at other electromorphic loci. Gene frequency data are reported for seven electromorphic loci in An. minimus sensu lato from eleven localities: one of the newly recognized species predominated in all but one locality and the second was confined to two localities. This species pair of An. minimus s.l. was clearly distinguished from An. aconitus Dönitz, An. pampanai Büttiker & Beales and An. varuna Iyengar, three species closely related to An. minimus s.l. in the series Myzomyia of Anopheles subgenus Cellia.

Secondary sympatric occurrence of sibling species of subterranean shrimps in the Karst

Allozyme variation at 32 gene loci was studied in cave dwelling shrimps of the genus Troglocaris (fam. Atyidae). Populations were collected from several caves and wells belonging to different drainage systems in the Karst areas of NE Italy. Results suggest the existence of two sympatric, genetically distinct, biological species (provisionally indicated as species A and B in the T. anophthalmus complex) in the samples collected at the Duino Well, Sagrado and Comarie caves (Nei’s `D= 0.209). Samples from Gradisca and Aurisina are represented by only one (A) or the other (B) of the two species, respectively. Two remaining eastern populations from the Rosandra Valley also proved to be monospecific. However, they posses fixed alternative alleles markedly different from both species A and B suggesting that these two populations may belong to a third sibling species, C (A vs. C, `D = 0.346; B vs. C, `D =0.146). These data are discussed in relation to allopatric speciation of cave dwelling shrimp species, flooding periods of subterranean waters and the role of cave organisms as markers of this process.

Genetically distinct sympatric populations of resident and anadromous Atlantic salmon, Salmo salar

Atlantic salmon (Salmo salar) from Little Gull Lake on the Gander River system of central Newfoundland were found to be electrophoretically polymorphic at 5 of 20 protein loci screened. Four of the polymorphic loci were structural and one was regulatory. Major heterozygote deficiencies relative to Castle–Hardy–Weinberg expectations were detected at the two most polymorphic loci, Aat-3 and Mdh-3,4, and significant nonrandom associations between genotypes at these loci and the other polymorphic loci, Sdh-1, Me-2, and Pgm1-t, were also found. The heterozygote deficiencies and the nonrandom genotype associations were attributable to the admixture of genetically distinct gene pools of resident and anadromous salmon in the lake. This is the first documented case of coexistence of reproductively separated populations of Atlantic salmon of the two life history types, and shows that the sympatric occurrence of the two forms can represent between-population variation.

Diatom assemblies in some moorland pools in the Drenthian district (the Netherlands)

The results are presented of a survey of diatom assemblies in a number of moorland pools and lakes in the Dwingeloo area of Drenthe. Four assemblies, with some intermediate ones, are described. (1) An assembly characterized by an abundance ofFrustulia rhomboides var.saxonica, Eunotia lunaris, E. veneris var.rhomboidea andTabellaria flocculosa and found in oligotrophic water with a pH in the range 3.1–4.2 (2) An assembly solely consisting ofEunotia exigua which occurs in oligo-minerotrophic pools with brownish deposits of iron compounds and a pH of about 3.5. (3) An assembly consisting of 100%Eunotia paludosa found in the ombrotrophic habitat of emerged stands ofSphagnum with a pH averaging 3.1. This species was found in nearly all localities sampled. (4) An assembly characterized by the sympatric occurrence ofMelosira italica, Nitzschia gandersheimiensis, Gomphonema parvulum andTabellaria flocculosa and found in mesotrophic, disturbed habitats with an average pH of about 4.5. For the delimitation of these assemblies a cluster analysis was carried out by means of the TABORD computerprogram.

Calamagrostis hakonensis (Poaceae): Distribution and differentiation of cytotypes

Chromosome counts were made for a total of 540 collections ofCalamagrostis hakonensis from 66 localities ranging from Kyushu to Hokkaido. Distribution and habitat preferences of the cytotypes involved are described. Sympatric occurrence of tetraploids (=semidiploids, 2n=28) and higher polyploids, as well as that of septaploids and plants at hexaploid and/or octoploid levels, was confirmed in several localities, and mixtures of hexaploids and octoploids within a population were frequently observed. Plants at hexaploid and octoploid levels were the most abundant and widespread. An examination of pollen of the voucher specimens showed that tetraploids (amphimictic) had good pollen, while higher polyploids (apomictic) were generally devoid of pollen and very rarely produced moderately good pollen, the grains of higher polyploids being larger than those of tetraploids. Distributions of tetraploids and higher polyploids were more precisely delineated through an examination of pollen of many herbarium specimens. In relation to the processes by which the complicated internal structure ofC. hakonensis has been established, the following subjects are discussed: infraspecific hybridization between ecotypically differentiated populations, enrichment of variability through occasional sexual reproduction expected in plants with more than 2n=42, persistence of the variants by apomictic reproduction, and probable roles of some extinct taxa.

A Late Weichselian find of polar bear (Ursus maritimus Phipps) from Denmark and reflections on the paleoenvironment

The mandible of a polar bear (Ursus maritimus Phipps) found in about 1920 at Kjul Å, North Jutland, and described by Nordmann & Degerbol in 1930. has been l4C dated to 11.100 ± 160 B.P. It is so far the only find of polar bear in Denmark. Comparison with recent 14C datings of Swedish and Norwegian polar bears shows that the Danish specimen was a member of a southern Scandinavian Late Weichselian population. The contemporaneous Zirphaeu sea deposits can be regarded as the boreal‐arctic shallow water equivalent of the arctic Upper Saxicava sand deposits from northern Jutland. The polar bear mandible, however, was deposited on land, as was the metacarpal bone of a brown bear (Ursus arctos) from the nearby Nr. Lyngby locality of Allerød age. The overall picture of the Late Weichselian mammal fauna in Denmark shows a mixed composition of different ecotypes. Their sympatric occurrence points at a unique environment not comparable to any now existing, and probably related to the very low latitude of the Weichselian ice sheet.

Genetic Variation in a Dwarfed Lineage, the Mexican Salamander Genus Thorius (Amphibia: Plethodontidae): Taxonomic, Ecologic and Evolutionary Implications

Patterns of genetic relationship and taxonomic identity are examined in Thorius, an enigmatic genus of minute neotropical salamanders that represent the smallest tailed tetrapods. Data comprise an electrophoretic analysis of 16 protein loci in 69 population samples from 55 localities throughout the range of the genus in southern Mexico. Eight of the nine described species are genetically distinct: Nei's D commonly exceeds 0.9. There is no biochemical evidence of more than a single species at Zoquitlan, Pue., type locality of T. schmidti and T. maxillabrochus. Genetic differentiation between disjunct subspecies of T. pennatulus is less than the mean pairwise value between described species, but exceeds that observed between some sympatric species pairs. Seven additional as yet undescribed species are identified, based either on their sympatric occurrence with, or great genetic differentiation from, described species. Most species initially identified by electrophoresis are morphologically distinct. Electrophoretic data fail to resolve the taxonomic affinity of a few remaining populations, although they do provide clearcut and distinguishable hypotheses of relationship that can be tested using other sources, such as morphology. The 15 species constitute three faunal units: Veracruz and eastern Puebla; Sierra de Juarez, Oaxaca; southern and western Oaxaca, and Guerrero. Local endemism is observed within each region, in which sympatry involving two or three species is common. Species frequently demonstrate narrow elevational zonation and distinct habitat and microhabitat preference (e.g., arboreal vs terrestrial). The distribution of four species on Cerro Pelon, Oax., is examined in detail.

Variation and systematics of frogs of the Genus Cycloramphus (Amphibia, Leptodactylidae)

Variation is analyzed among members of the Neotropical frog genus Cycloramphus. The results of the analyses of variation are used in part to delimit species. Twenty one species are recognized, nine of them are described as new. The genus Craspedoglossa is considered a synonym of Cycloramphus. The genus Scythrophrys is not closely related to Cycloramphus, but the genus Zachaenus is. A definition for the genus Cycloramphus is provided, as are taxonomic summaries for each species. The species accounts include a skeletal synonymy, diagnosis of adults, a morphological definition of adults and larvae where known, an advertising call description and a distributional summary with localities and maps. A detailed description of the holotype is provided for each new species. A key to the species distinguishes adult specimens of Cycloramphus. Much of the interspecific variation is of about the same magnitude as intraspecific variation. Natural selection has resulted in changes of both size and shape among species of the genus Cycloramphus. There are no universal patterns of species differentiation and sympatric occurrence. The kinds and degrees of differences among species appear to be geographically specific.

Adaptation and Dimorphism in Eastern Hemlock, Tsuga canadensis (L.) Carr

Eastern hemlock's (Tsuga canadensis (L.) Carr.) habitat distribution, and variations in its growth rate response to macroclimatic variation, sensitivity to climatic and topographic variation, and gross needle and branch morphology, were quantified in eight major geographical areas throughout the species' range in the eastern United States. The results revealed two apparent sympatric ecotypes or morphs which occur throughout most of the species' range; these ecotypes may be differentiated by habitat preference, growth rates, sensitivity to moisture and temperature, and certain gross morphological characters. The "high-response" hemlock prefers mesophytic habitats, and exhibits a high growth rate, high sensitivity to moisture, and low sensitivity to temperature. The "low-response" type also occurs in mesic sites, but is more common on subxeric slopes; it exhibits a low growth rate, low sensitivity to moisture, and high sensitivity to temperature. Throughout southern Canada and New England, the two ecotypes are distinct in terms of growth rate, morphology, and response to macroclimatic variation, despite their sympatric occurrence in mesophytic habitats; only limited intergradation is observed. In the Alleghenies and southern Appalachians, the two types broadly intergrade, providing a spectrum of phenotypes, the extremes of which correspond to the two New England ecotypes. Only the high-response type was found in the Cumberland Mountains and Plateau, while the disjunct populations studied in Indiana were composed entirely of intermediate individuals. Differentiation into ecotypes and subsequent introgression between the two ecotypes appear to confirm a competitive advantage to T. canadensis, giving it a phenotypic elasticity which allows it to occupy a broad range of habitats. However, there also appears to be sufficient divergent selection against the intermediates to prevent the two ecotypes' convergence or fusion into a single phenotype.

CYTOLOGICAL AND ECOLOGICAL NOTES ON THE TARAXACUM SECTIONS ERYTHROSPERMA AND OBLIQUA OF THE COASTAL AREA OF THE NETHERLANDS

SUMMARY In this first publication of a series reporting on the results of a biotaxonomic and ecological research project concerning the genus Taraxacum, cytological and some oecological data are recorded of 13 species belonging to the sections Erythrosperma and Obliqua from the dune area of the province of N. Holland and from the North Sea island of Terschelling (The Netherlands), are recorded. In most of the population samples from 4 to 8 different species were found. The populations from the mainland proved to be richer in species than those of Terschelling. Some ecological and possible genetic implications of the sympatric occurrence of so many species in the same habitat are discussed. The chromosome numbers of T. commixtum (2n = 24,32) and of T. laetiforme (2n = 24) had not previously been determined. In four other species chromosome numbers were found which differ from counts of the same species as reported in the literature. Both the local and the regional karyological variation are appreciable. There is a remarkable concentration of (newly recorded) tetraploid forms in a restricted area within the mainland area studied. A study of the chromosome morphology revealed a most inconsistent pattern of satellites and secondary constrictions within a single species, involving both their number and their size or location. In the discussion some attention has been paid to the conceivably erroneous reports in the literature of hypertriploidy which may be attributable to this inconsistency of the chromosome morphology.