Speciation and adaptive radiation of subterranean mole rats, Spalax ehrenbergi superspecies, in Jordan

The major initial mechanism of speciation in subterranean blind mole rats, Spalacidae, is chromosomal, primarily through Robertsonian rearrangements. Here we highlight another scenario of chromosomal rearrangement leading to ecological speciation and adaptive radiation apparently initiated by pericentric inversions and genie divergence to different ecologies in mole rats in Jordan. We analysed karyotype, allozyme, size and ecological diversity across the range of mole rats in Jordan from mesic Irbid in the north to xeric Wadi Musa (Petra region) in the south, a transect of 250 km. We examined mole rats for chromosome ( N =71), size ( N =76), and allozyme ( N =67) diversities, encoded by 32 loci, in 12 populations of the Spalax ehrenbetgi superspecies in Jordan. By a combination of chromosome morphology, genetic distance, body size and ecogeography, we identified four new putative biological species. All species (except two animals in Madaba) share 2 n = 60 but vary in chromosome morphology, caused by pericentric inversions and/or centromeric shifts. The 'north Moav' species is karyotypically polymorphic for 2 n (2 n = 60; including locally also two animals with 2 n = 62). The distribution of the four species is associated with ecogeographical different domains and climatic diversity. Genetic diversity indices were low, but like chromosome arms (NFa) were positively correlated with aridity stress. Discriminant analysis correctly classified 91% of the individuals into the four species utilizing combinatorially chromosome, allozyme and size diversities. It is hypothesized that mole rat evolution underground is intimately associated with climatic diversity stress above ground.     

Observations of Chromosomes of Malus Species in China

Somatic chromosome numbers of 37 forms (representing 22 species) of apples in China were counted using wall-degradation and hypotonic method. Among the species investigated 3 categories of chromosome numbers, i.e. 2n=34, 51 and 68 are confirmed. The chromosome numbers of the following species are here first reported: Malus ombrophila 2n= 34, M. prattii 2n=34, M. melliana 2n=34, Zhaojiaohonghua (M. sp.) 2n=34, and M. asiatica var. 2n=68. Polyploids (including infraspecific polyploids) account for 41% of the total number of the species investigated. 51 is a predominant number. It is suggested that ploidy variation is an important pathway in apple evolution in China, and triploid may be considered as a suitable evolution grade. There are rich apple germplasm resources in China. The systematic studies of this genus are obviously essential.     

The occurrence of Cryptocoryne and Lagenandra (Araceae) on Sri Lanka

Depending on the species, Cryptocoryne plants grow in different biotopes, viz. spring, river, dark forest, and tree-savanna. The species of Lagenandra are exclusively found in river biotopes. The chromosome numbers found in this study corroborate the numbers previously recorded. Some variation in respect to the morphology of the inflorescence of C. wendtii de Wit and L. ovata (L.) Thwaites is described. A map presenting the distribution of the of Cryptocoryne with their chromosome numbers is included.
The existing populations of Cryptocoryne on Sri Lanka should be protected from further exploitation by plant collectors.     

Allozyme differentiation of various chromosomal forms of the spotted suslik (Spermophilus suslicus Guld, 1770, Rodentia)]

Eleven enzyme and four nonenzyme protein systems controlled by 25 loci were electrophoretically analyzed in the allopatric karyotypic forms (2n = 34 and 2n = 36) of the spotted souslik Spermophilus suslicus. Genetic variability and differentiation for the forms with different chromosome sets were estimated. Two discriminative loci (Alb and Tf) for the studied chromosome forms were found. The UPGMA dendrogram was constructed, which summarizes genetic (allozyme) relationships found for the forms of the spotted souslik with different chromosome sets. Subdividing the species into two karyotypic forms was shown to be followed by differentiating these forms at the allozyme level.     

Analysis of intraspecific divergence of hexaploid wheat Triticum spelta L. by chromosome C-banding

Intraspecific divergence of hexaploid wheat Triticum spelta was studied by chromosome C-banding in 41 accessions of different geographic origins. The spelt accessions did not differ in karyotype structure or heterochromatin distribution from common wheat, but showed greater intraspecific polymorphism for chromosome rearrangements (translocations, inversions) and banding patterns. On evidence of C-banding patterns, spelt was assumed to occupy an intermediate position between tetraploid and hexaploid wheat species. Accessions of the Asian spelt subspecies had more diverse banding patterns than European accessions. A relatively high frequency of chromosome rearrangements was observed in Iranian accessions. Visual analysis revealed high uniformity of chromosome banding patterns in T. spelta populations of Afghanistan, Spain, and Germany (Bavarian group), suggesting a significant role of the founder effect in their evolution.     

Restriction endonuclease and molecular analyses of three rat genomes with special reference to chromosome rearrangement and speciation problems

When differences are found between related species of organisms, it is often assumed that the differences themselves are causal factors either in speciation itself or in processes related to speciation. Two recent proposals on the functions of satellite DNA (Hatch et al., 1976 and Fry and Salser, 1977) are that (a) large amounts of satellite DNA are important in facilitating chromosome rearrangements and hence cytogenetic evolution, and (b) satellite DNA differences between homologous chromosomes lead to pairing difficulties and are important in generating infertility barriers and hence speciation. If these proposals were to have some generality, one could expect organisms with very low amounts of highly repeated DNA to exhibit few chromosome rearrangements and to be evolutionarily conservative in a cyto-genetic sense. — We have chosen two very closely related species of rat which are phenotypically almost indistinguishable and which have undergone massive genome reorganization. They differ by 11 major centric rearrangements (2n=32, 2n=50). We have characterised their genomes by restriction endonuclease digestions, thermal denaturations, analytical ultracentrifugations and reassociation techniques, and have found that they have virtually no highly repeated DNA. Thus the 11 major chromosomal rearrangements have been fixed in present day genomes with hardly any highly repeated DNA, centric or otherwise. — It appears therefore that a large amount of highly repeated DNA is not obligatory for the formation and fixation of chromosome rearrangements. In addition, the existing literature reveals that one can find almost any situation at all, from species groups with high amounts of satellite DNA and no gross chromosomal rearrangements, to ones such as those described here, with tiny amounts of highly repeated DNA and massive chromosomal reorganisation. Since direct experimental data indicates that satellite DNA differences per se between homologous chromosomes do not cause infertility, speculations concerning modes of speciation based on satellite DNA differences between otherwise homologous chromosomes would appear to be ill founded.     

Mapping the distribution of the telomeric sequence (T(2)AG(3))(n) in rock wallabies,Petrogale (Marsupialia: Macropodidae), by fluorescence in situ hybridization. ii. the lateralis complex

The distribution of the conserved vertebrate telomeric sequence (T(2)AG(3))(n) was examined by fluorescence in situ hybridization in the six Petrogale (rock wallabies) taxa of the lateralis complex. As expected, the (T(2)AG(3))(n) sequence was located at the termini of all chromosomes in all taxa. However, the sequence was also present at several nontelomeric (viz., interstitial and centromeric) sites. The signals identified were associated with either ancient rearrangements involved with the formation of the 2n = 22 plesiomorphic macropodine karyotype or more recent rearrangements associated with karyotypes derived from the 2n = 22 karyotype. Interstitial (T(2)AG(3))(n) signals identified on chromosomes 3 and 4 in all six species of the lateralis complex and a large centromeric signal identified on chromosome 7 in the five subspecies/races of P. lateralis appear to be related to the more ancient rearrangements. Subsequent chromosome evolution has seen these signals retained, lost, or amplified in different Petrogale lineages. Within the lateralis complex, in two submetacentric chromosome derived by recent centric fusions, the telomeric sequence was identified at or near the centromere, indicating its retention during the fusion process. In the two taxa where chromosome 3 was rearranged via a recent centromeric transposition to become an acrocentric chromosome, the telomeric signal was located interstitially.     

Molecular characterisation and evolution of the hemocyanin from the European spiny lobster,<Emphasis Type="Italic"> Palinurus elephas</Emphasis>

The hemocyanin of the European spiny lobster Palinurus elephas (synonym: Palinurus vulgaris) is a hexamer composed by four closely related but distinct subunits. We have obtained the full cDNA sequences of all four subunits, which cover 2275-2298 bp and encode for native polypeptides of 656 and 657 amino acids. The P. elephas hemocyanin subunits belong to the alpha-type of crustacean hemocyanins, whereas beta- and gamma-subunits are absent in this species. An unusual high ratio of non-synonymous versus synonymous nucleotide substitutions was observed, suggesting positive selection among subunits. Assuming a constant evolution rate, the P. elephas hemocyanin subunits emerged from a single hemocyanin gene around 25 million years ago. The alpha-type hemocyanins of P. elephas and the American spiny lobster Panulirus interruptus split around 100 million years ago. This is about five times older than the assumed divergence time of the species and suggests that the genera may have split with the formation of the Atlantic Ocean. The application of the Bayesian method for phylogenetic inference allows for the first time a solid reconstruction of the evolution of the decapod hemocyanins, showing that the beta-subunit types diverged first and that the crustacean pseudo-hemocyanins are associated with the gamma-type subunits.     

The effects of food presentation and microhabitat upon resource monopoly in a ground-foraging ant (Hymenoptera: Formicidae) community

In Neotropical wet forests several species of omnivorous, resource-defending ants, live and forage in close proximity to one another. Although the forest floor is heterogeneous in microhabitat and food quantity, little is known about the impact of microhabitat and food variation upon resource monopoly among ants. We investigated how food type and microhabitat influence food monopoly in resource-defending ants in old-growth tropical wet forest in the Caribbean lowlands of Costa Rica. We measured several microhabitat characteristics at 66 points in a 0.5 hectare plot, and baited each point with two categories of tuna bait. These baits were presented in "split" and "clumped" arrangements. We measured the frequency of bait monopoly by a single species, as well as the number of recruited ant foragers at a bait. Out of five common species, two (Wasmannia auropunctata and Pheidole simonsi) more frequently monopolized one bait type over the other, and one (P. simonsi) recruited more ants to the split baits. We then considered the recruitment response by all ant species in the community. We found that the frequency of monopoly, sharing, and the absence of ants at a given point in the rainforest differed with bait type. The frequency of monopoly was associated with microhabitat type in two out of eight microhabitat variables (leaf litter depth and palms); variation in two other types (canopy tree distance and leafcutter ant trails) was associated with changes in forager number. In at least two ant species, food presentation affected monopoly at baits; among all resource-defending ants, the microhabitats where ants foraged for food and the type of food located determined in part the frequency of monopoly and the number of foragers at the food item. These results suggest that the location and presentation of food items determines in part which ant species will utilize the resource.     

Homogeneity of recombination rate within a conserved region on BTA3 that contains QTL

The D3S20-D3S34-D3S3 region on BTA3 contains quantitative trait loci (QTL) controlling milk production traits. This region also displays extensive conservation of synteny among several species including cattle, humans, mice and sheep. In this study, we evaluated the adjacent intervals D3S20-D3S34 and D3S34-D3S3 for differences in recombination rate (theta) among bulls in order to assess the suitability of population-based estimates of theta for marker assisted selection and to explore the relationship between variation in theta and chromosome breakpoints associated with mammalian evolution. Using sperm typing, thetaD3S20-D3S34 and theta D3S34-D3S3 were estimated for six triply heterozygous bulls. Recombination frequency ranged from 6.2 to 12.5% and from 9.7 to 19.2% for the D3S20-D3S34 and D3S34-D3S3 intervals, respectively. However, significant variation in theta was not detected between bulls for either interval (D3S20-D3S34 chi(2)5 d.f.=2.59, P < 0.90; D3S34-D3S3 chi(2)5 d.f.=3.72, P < 0.75). The observed differences in theta were most readily attributed to differences in allele-specific amplification efficiencies among bulls. Our results suggest that the positions of QTL in this region can be reliably determined from population data and therefore accurate marker-assisted selection can be performed for desirable alleles without concern for variation in theta. Furthermore, when considered with results of earlier studies, these findings support a correlation between the existence of evolutionary breakpoints or chromosome rearrangements and variation in theta.     

Chromosomal rearrangements in rock wallabies, Petrogale (Marsupialia: Macropodidae). VII. G-banding analysis of Petrogale brachyotis and P. concinna: species with dramatically altered karyotypes.

G-banded metaphase preparations of cultured fibroblasts were used to construct the karyotypes of Petrogale brachyotis (2n = 18) and P. concinna (2n = 16). The two karyotypes differ significantly from the plesiomorphic karyotype of the genus and from those of all other Petrogale species examined. Petrogale brachyotis and P. concinna are characterised by three synapomorphies: a 1-10 centric fusion, a 3a-6 centric fusion, and a submetacentric chromosome 2 (2s). Both species also possess autapomorphies. Petrogale brachyotis is characterised by submetacentric chromosomes 5 (5s) and 4 (4sm), whereas P. concinna is characterised by a 5-9 centric fusion and a submetacentric chromosome 8 (8m). The 2s, 5s, 4sm, and 8m chromosomes all appear to be derived from their plesiomorphic homologs by centromeric transpositions. Although the rate of chromosome evolution varies considerably in Petrogale, the genus clearly exhibits karyotypic orthoselection, with all the autosomal rearrangements identified being either centric fusions or centromeric transpositions. This study also illustrates the potential for convergent evolution in chromosomally diverse groups and demonstrates the importance of G-banding studies for accurate identification of chromosome rearrangements.     

X-chromosomal localization of mammalian Y-linked genes in two XO species of the Ryukyu spiny rat

Ryukyu spiny rats (genus Tokudaia), which are endemic to the central part of the Nansei Shoto archipelago in Japan, have unique karyotypes with odd numbers of chromosomes and no cytologically recognizable Y chromosome. The chromosome numbers of Tokudaia osimensis from Amamioshima and of Tokudaia sp. from Tokunoshima are 2n = 25 and 2n = 45, respectively, with a putative single X chromosome. The mouse X probe hybridized to the unpaired X chromosome, except for the distal part of the short arm in a female specimen of T. osimensis and in one male and one female of Tokudaia sp. Fluorescence in situ hybridization with the Tspy (testis-specific protein, Y-encoded) gene from both male and female cells of Tokudaia sp. by PCR localized Tspy to the distal part of the long arm of the X chromosome. Another Y-related gene, Zfy, from Tokudaia sp. was also localized to the same region in both species. Although the Sry gene is absent in this species, the present results suggest that the Y-chromosome segment carrying functional Y-linked genes, such as Tspy and Zfy, is translocated onto the distal part of the long arm of the X chromosome.     

Extensive chromosomal rearrangements and nuclear DNA content changes in the evolution of the armoured catfishes genus Corydoras (Pisces, Siluriformes, Callichthyidae)

Karyotypes and nuclear DNA content were studied in 11 species of the genus Corydoras from rivers in South America: C . sp. from Caripi river 2 n =60, C . cf. simulatus 2 n =62, C . simulatus 2 n =62, C . reticulatus 2 n =74, C . sp. from Galheiro river 2 n =84, C . aff. punctatus from Negro river 2 n =102, C . flaveolus 2 n =58, C . arcuatus 2 n =46, C . trilineatus 2 n =46, C . schwartzi 2 n =46, and C . metae 2 n =92. Extensive chromosome diversity and differences in DNA content were detected among species. The high variability in chromosome counts was not exclusively related to chromosomal structural rearrangements, but also to large changes in DNA content. Species could be grouped using their shared cytogenetic characteristics, suggesting that within the genus Corydoras different groups of species followed distinct evolutionary trends. Chromosomal rearrangements in Corydoras are, apparently, more frequent that morphological modifications, so cytogenetic data may be very useful for species delimitation and for the understanding of interrelationships among species.     

Coccidian parasites (Apicomplexa: Eimeriidae) from insectivores. III. Seven new species in shrews (Soricidae: Soricinae) from Canada, Japan, and the United States

Since May 1979, 458 shrews (Blarina sp. and Sorex spp.) representing 20 species collected in Canada, Japan, and the United States were examined for coccidia; 110 (24%) had oocysts in their feces, including 8 of 21 (38%) B. brevicauda from Massachusetts, Ohio, Pennsylvania, and Vermont; 2 of 7 (29%) S. caecutiens from Hokkaido and Honshu; 14 of 63 (22%) S. cinereus from Colorado, New Mexico, Pennsylvania, Vermont, Manitoba, and Ontario; 3 of 7 (43%) S. fontinalis from Pennsylvania; 11 of 16 (69%) S. fumeus from Massachusetts, Minnesota, Pennsylvania, Vermont, and Ontario; 1 of 4 (25%) S. haydeni from Minnesota; 6 of 8 (75%) S. longirostris from Florida and Virginia; 1 of 2 (50%) S. ornatus from California; 5 of 12 (42%) S. pacificus from California and Oregon; 13 of 41 (32%) S. palustris from California, Colorado, and New Mexico; 1 of 2 (50%) S. tenellus from California; 11 of 105 (10%) S. trowbridgii from California, Oregon, and Washington; 10 of 48 (21%) S. unguiculatus from Hokkaido; and 24 of 112 (21%) S. vagrans from Arizona, California, Colorado, New Mexico, Oregon, and Washington. The following coccidians were identified from infected shrews: Eimeria brevicauda n. sp. from B. brevicauda; Eimeria fumeus n. sp. from S. fumeus, S. pacificus, S. unguiculatus, and S. vagrans; Eimeria inyoni n. sp. from S. tenellus; Eimeria palustris n. sp. from S. cinereus, S. fontinalis, S. fumeus, S. haydeni, S. longirostris, S. ornatus, S. pacificus, S. palustris, S. tenellus, S. trowbridgii, and S. vagrans; Eimeria vagrantis n. sp. from S. fumeus, S. trowbridgii, and S. vagrans; Isospora brevicauda n. sp. from B. brevicauda; and Isospora palustris n. sp. from S. pacificus, S. palustris, S. trowbridgii, S. unguiculatus, and S. vagrans. The world literature on coccidian parasites of shrews (16 eimerians and 3 isosporans exclusive of the 7 new species described here) is reviewed.     

Population genetic structure of two ecologically distinct Amazonian spiny rats: separating history and current ecology

Abstract. Population history and current demographic and ecological factors determine the amount of genetic variation within and the degree of differentiation among populations. Differences in the life history and ecology of codistributed species may lead to differences in hierarchical population genetic structure. Here, we compare patterns of genetic diversity and structure of two species of spiny rats in the genus Proechimys from the Rio Jurua of western Amazonian Brazil. Based on the ecological and life-history differences between the two species, we make predictions as to how they might differ in patterns of genetic diversity and structure. We use mitochondrial sequence data from the cytochrome b gene to test these predictions. Although both species maintain nearly the same number of mitochondrial haplotypes across the sampled range, they differ in levels of genetic diversity and geographic structure. Patterns of gene flow are also different between the two species with average M-values of nearly three in P. steerei and less than one in P. simonsi . Our initial predictions are largely upheld by the genetic data and where conflicting hypotheses arise, we suggest further studies that may allow us to distinguish among evolutionary scenarios. Separating the effects of history and ongoing demography on patterns of genetic diversity is challenging. Combining genetic analyses with field studies remains essential to disentangling these complex processes.     

The reproductive tract of the male spiny mouse (Acomys cahirinus) and coagulation studies with other species

The testes of the spiny mice showed asymmetry, the left being significantly heavier than the right (P = 0.025). Histological studies indicated that spermatozoa were first present in the testes of animals 35--45 days of age but the maturation of the accessory glands, especially the lateral prostates and coagulating glands, occurred later. The highest fructose concentration in the adult was in the lateral prostates (126.97 +/- 22.23 mg fructose/100 g, n = 5) and coagulating glands (99.38 +/- 17.65 mg fructose/100 g gland weight, n = 5). Coagulation tests of mixtures of extracts of seminal vesicles and coagulating glands from spiny mice and rats indicated that the vesiculase of the spiny mouse was active on rat substrates and vice versa. Cross-reactions of extracts of house mouse (Mus musculus), hamster (Mesocricetus auratus), gerbil (Meriones unguiculatus), and guinea-pig (Cavia porcellus) seminal vesicles (substrate) and coagulating glands (vesiculase) with those of rats and spiny mice showed that although the substrates of rat and spiny mouse were readily coagulated by vesiculase from all the other species, rat and spiny mouse vesiculase were not equally active on substrates of the other species.     

Chromosomal homologies among vampire bats revealed by chromosome painting (phyllostomidae, chiroptera)

Substantial effort has been made to elucidate karyotypic evolution of phyllostomid bats, mostly through comparisons of G-banding patterns. However, due to the limited number of G-bands in respective karyotypes and to the similarity of non-homologous bands, an accurate evolutionary history of chromosome segments remains questionable. This is the case for vampire bats (Desmodontinae). Despite several proposed homologies, banding data have not yet provided a detailed understanding of the chromosomal changes within vampire genera. We examined karyotype differentiation of the 3 species within this subfamily using whole chromosomal probes from Phyllostomus hastatus (Phyllostominae) and Carollia brevicauda (Carolliinae). Painting probes of P. hastatus respectively detected 22, 21 and 23 conserved segments in Diphylla ecaudata, Diaemus youngi, and Desmodus rotundus karyotypes, whereas 27, 27 and 28 were respectively detectedwith C. brevicauda paints. Based on the evolutionary relationships proposed by morphological and molecular data, we present probable chromosomal synapomorphies for vampire bats and propose chromosomes that were present in the common ancestor of the 5 genera analyzed. Karyotype comparisons allowed us to relate a number of conserved chromosomal segments among the 5 species, providing a broader database for understanding karyotype evolution in the family.     

蝴蝶在生境和生物小区之间的移位伴随着对外来蜜源的利用

在发育成熟的温带环境中,植食性昆虫群落能迅速适应引入植物并将其作为幼虫的食物和花蜜.我们研究了经过森林砍伐的热带环境中蝴蝶对利用引入植物作为蜜源植物的适应快慢程度,并研究了蝴蝶-显花植物在新的生物小区中出现的范围,发现蝴蝶对引入显花植物的利用和探访多于本地植物,这与引入植物在调查地点、生物小区和植物丰度中的普遍性有关.此外,取食花蜜的蝴蝶和显花植物与正在形成的的生物小区有关,例如路边、农田、集约耕地以及花园.在这些新生物小区中,引入植物很重要,因为它们为蝴蝶提供了蜜源.     

Mechanisms of chromosomal evolution and its possible relation to natural history characteristics in Ancistrus catfishes (Siluriformes: Loricariidae)

Ancistrus is the most speciose genus of the tribe Ancistrini, with 58 valid species and many yet to be described. Cytogenetic studies were conducted on five apparently undescribed species from the Amazon basin, which showed different diploid numbers: Ancistrus sp. Purus (2n = 34); Ancistrus sp. Macoari (2n = 46); Ancistrus sp. Dimona (2n = 52); Ancistrus sp. Vermelho (2n = 42) and Ancistrus sp. Trombetas (2n = 38). All species possessed only one pair of NOR‐carrying chromosomes, but with extensive variation in both the location on the chromosome as well as in the position of the ribosomal sites on the karyotype. The karyotypic evolution of Ancistrus species seems to be based on chromosomal rearrangements, with a tendency to a reduction of the diploid number. Two new instances of XX/XY sex chromosomes for Ancistrus species, based on the heteromorphism in the male karyotype, were also recorded. The large karyotypic diversity among Ancistrus species may be related to biological and behavioural characteristics of these fish that include microhabitat preferences, territoriality and specialized reproductive tactics. These characteristics may lead to a fast rate of fixation of chromosomal mutations and eventually speciation across the basin.     

Reciprocal chromosome painting shows that the great difference in diploid number between human and African green monkey is mostly due to non-Robertsonian fissions

We used reciprocal chromosome painting with both African green monkey (C. aethiops) and human chromosome specific DNA probes to delineate homologous regions in the two species. Probes were derived by fluorescence-activated chromosome flow sorting and then were reciprocally hybridized to metaphase spreads of each species. Segments in the size range of a single chromosome band were identified, demonstrating the sensitivity of the approach when comparing species that diverged more than 20 million years ago. Outgroup analysis shows that the great difference in diploid numbers between the African green monkey (2n = 60) and humans (2n = 46) is mainly owing to fissions, and the direction of change is towards increasing diploid numbers. However, most break points apparently lie outside of the centromere regions, suggesting that the changes were not solely Robertsonian as has been previously assumed. No reciprocal translocations have occurred in the phylogenetic lines leading to humans or African green monkeys. The primate paints established here are a valuable tool to establish interspecies homology, to define rearrangements, and to determine the mechanisms of chromosomal evolution in primate species. Received: 10 December 1998 / Accepted: 18 February 1999