Ancient hybrid origin of the eastern wolf not yet off the table: a comment on Rutledge et al. (2015)

A recent study of North American canids by Rutledge et al. (Biol. Lett. 11, 20150303 (doi:10.1098/rsbl.2015.0303)) refutes the hypothesized hybrid origin of the eastern wolf (EW) based on genomic evidence against very recent hybridization. However, the analyses do not rule out the possibility of more ancient hybridization. Claims to have resolved the evolutionary origin of the EW are therefore inappropriate. Importantly, though, we plead that uncertainty about the ancient history of the taxon should not affect current conservation policy.     

Identification of microsatellite sequences in Vitis riparia and their applicability for genotyping of different Vitis species.

A Vitis riparia genomic library was screened for the presence of (GA)n simple sequence repeats (SSR) and 18 primer pairs yielding amplification products of the expected size were designed. Heterologous amplification with the primer pairs in related species (V. rupestris, V. berlandieri, V. labrusca, V. cinerea, V. aestivalis, V. vinifera, and interspecific hybrids) was successful in most primer-species combinations. Therefore, the new markers are applicable to the genotyping of a range of Vitis species. Variations in the SSR flanking sequence were detected between and within the species. The degree of polymorphism and performance of the markers were determined in up to 120 individuals of V. vinifera. Four of fifteen alleles per locus were detected and expected heterozygosity ranged between 0.37 and 0.88. Null alleles were shown to be present at two loci by a lack of heterozygous individuals and by transmission of the null alleles in a controlled cross. Regular Mendelian inheritance is indicated for all but one loci by a preliminary segregation analysis in 36 offspring. Thirteen of the markers were found suitable for the genotyping of grapevines (V. vinifera).     

Phylogeographic history of the genus Tropheus,a lineage of rock-dwelling cichlid fishes endemic to Lake Tanganyika

Lake Tanganyika contains the oldest and most complex flock of cichlid fishes counting about 200 endemic species. It is comprised of 16 ecologically, morphologically and genetically highly distinct tribes. Many species are further subdivided into arrays of geographic morphs, each colonizing particular sections of the shore line. The genus Tropheus represents the most spectacular and best studied example for this phenomenon, counting more than 100 distinctly colored populations and sister species, some living in sympatry. Their present distribution and genetic structure was shaped by a series of lake level fluctuations which caused cycles of isolation and secondary admixis. The present study extends previous work on the phylogeography of Tropheus and aims at the fine-scale reconstruction of the origin and spread of lineages in the central and southern basin of the lake. The previously defined mtDNA lineages were evaluated on the basis of statistical parsimony networks. Haplotype networks were created for each lineage and related to their centers of diversity in terms of present distribution. A linearized tree analysis and a mismatch distribution analysis corroborate two of the three radiation waves suggested in earlier works, but the new data suggest a different primary colonization scenario for the southern basin.     

A gene controlling sex in grapevines placed on a molecular marker-based genetic map.

Genetic maps of Vitis (2n = 38) have been constructed from an interspecific hybrid population of 58 seedlings of the cross 'Horizon' ('Seyval' x 'Schuyler') x Illinois 547-1 (V. cinerea B9 x V. rupestris B38). The maps were initially constructed based on 277 RAPD (random amplified polymorphic DNA) markers using a double-pseudotestcross strategy. Subsequently, 25 microsatellites, 4 CAPS (cleaved amplified polymorphic sequence), and 12 AFLP (amplified fragment length polymorphism) markers were added to the maps. Another 120 markers, mostly those segregating 3:1, were also assigned but not positioned on the linkage groups in the two maps. The 'Horizon' map consisted of 153 markers covering 1199 cM, with an average map distance of 7.6 cM between markers. The Illinois 547-1 map had 179 markers covering 1470 cM, with an average map distance of 8.1 cM. There were 20 linkage groups in each map, one more than the basic number of chromosomes in grapes. Ten linkage groups in each map were identified as homologous using 16 microsatellite and 2 CAPS markers polymorphic in both parents. A single locus controlling sex in grapes mapped close to a microsatellite marker. These maps provide enough coverage of the genome for QTL (quantitative trait loci) analysis and as a starting point for positional gene cloning in grapes.     

Separated by sand, fused by dropping water: habitat barriers and fluctuating water levels steer the evolution of rock-dwelling cichlid populations in Lake Tanganyika

The conditions of phenotypic and genetic population differentiation allow inferences about the evolution, preservation and loss of biological diversity. In Lake Tanganyika, water level fluctuations are assumed to have had a major impact on the evolution of stenotopic littoral species, though this hypothesis has not been specifically examined so far. The present study investigates whether subtly differentiated colour patterns of adjacent Tropheus moorii populations are maintained in isolation or in the face of continuous gene flow, and whether the presumed influence of water level fluctuations on lacustrine cichlids can be demonstrated in the small-scale population structure of the strictly stenotopic, littoral Tropheus. Distinct population differentiation was found even across short geographic distances and minor habitat barriers. Population splitting chronology and demographic histories comply with our expectation of old and rather stable populations on steeper sloping shore, and more recently established populations in a shallower region. Moreover, population expansions seem to coincide with lake level rises in the wake of Late Pleistocene megadroughts ~100 KYA. The imprint of hydrologic events on current population structure in the absence of ongoing gene flow suggests that phenotypic differentiation among proximate Tropheus populations evolves and persists in genetic isolation. Sporadic gene flow is effected by lake level fluctuations following climate changes and controlled by the persistence of habitat barriers during lake level changes. Since similar demographic patterns were previously reported for Lake Malawi cichlids, our data furthermore strengthen the hypothesis that major climatic events synchronized facets of cichlid evolution across the East African Great Lakes.     

Functional changes of the small intestine in over- and undernourished suckling rats support the development of obesity risk on a high-energy diet in later life

To investigate the relationship between early nutritional experience, ontogeny of the small intestinal functions and predisposition to obesity development, the following experimental models of male Sprague-Dawley rats were used: 1) rats in which the quantity of nutrition was manipulated from birth to weaning (day 30) by adjusting the number of pups in the nest to 4 (SL), 10 (NL) and 16 pups (LL) and 2) littermates of SL, NL and LL rats fed either a standard or a hypercaloric diet from days 80 to 135 of age. The overfed SL pups were overweight after day 15 and became permanently obese, whereas the underfed smaller LL pups, due to accelerated growth and enhanced food intake from day 30 to day 35, attained a body fat level that did not differ from normally fed NL rats. Moreover, a significantly increased duodenal and jejunal alkaline phosphatase (AP) activity was found in SL and LL rats and these acquired somatic and intestinal characteristics persisted from weaning throughout life. Eight weeks of high-energy diet feeding elicited a similar pattern of intestinal response in SL and LL rats that was clearly different from NL rats. Despite energy over-consumption in these three groups, both SL and LL rats still displayed enhanced AP activity and showed a significant increase in protein/DNA ratio accompanied with a significant body fat accretion. These results indicate that the postnatally acquired small intestinal changes induced by over- and undernutrition could be involved in the similar predisposition to obesity risk in later life when caloric density of the diet is raised.     

Parallel evolution of facial stripe patterns in the Neolamprologus brichardi/pulcher species complex endemic to Lake Tanganyika

Colour pattern diversity can be due to random processes or to natural or sexual selection. Consequently, similarities in colour patterns are not always correlated with common ancestry, but may result from convergent evolution under shared selection pressures or drift. Neolamprologus brichardi and Neolamprologus pulcher have been described as two distinct species based on differences in the arrangement of two dark bars on the operculum. Our study uses DNA sequences of the mitochondrial control region to show that relatedness of haplotypes disagrees with species assignment based on head colour pattern. This suggests repeated parallel evolution of particular stripe patterns. The complete lack of shared haplotypes between populations of the same or different phenotypes reflects strong philopatric behaviour, possibly induced by the cooperative breeding mode in which offspring remain in their natal territory and serve as helpers until they disperse to nearby territories or take over a breeding position. Concordant phylogeographic patterns between N. brichardi/N. pulcher populations and other rock-dwelling cichlids suggest that the same colonization routes have been taken by sympatric species and that these routes were affected by lake level fluctuations in the past.     

Variation of territory size and defense behavior in breeding pairs of the endemic Lake Tanganyika cichlid fish Variabilichromis moorii

Lake Tanganyika harbors the ecologically, morphologically, and behaviorally most diverse species flock of cichlid fishes. It is comprised by substrate breeding and mouthbrooding species, most of which live in littoral habitats. Species communities are characterized by complex behavioral and trophic interactions, resulting in a dense pattern of partially overlapping territories, depending on the degree of ecological distinctness. We studied territorial behavior of breeding pairs in a substrate breeding species, with respect to territory size and defense behavior. The study species Variabilichromis moorii belongs to the tribe Lamprologini, the most species rich tribe of cichlids in Lake Tanganyika. Our study shows that breeding pairs of V. moorii can have highly complex territories, in which both parents hold separate sub-territories which are shifted slightly according to the movements of the fry, but the outer borders are conjointly defended. The size of the total defended territory varied from <1 to almost 4 m², averaging at about 2 m². Depending on presence of competitors or fry-predators evoking agonistic interactions, the territory size varied quite substantially over the day. Attack rates and size of the defended area decreased with water depth. Agonistic behavior was observed toward heterospecifics as well as conspecifics, with heterospecific attacks mostly concerning territorial neighbors and potential fry-predators in about equal frequencies. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: T. Wilke, R. V?in?l? & F. Riedel Patterns and Processes of Speciation in Ancient Lakes: Proceedings of the Fourth Symposium on Speciation in Ancient Lakes, Berlin, Germany, September 4–8, 2006     

High frequency of multiple paternity in broods of a socially monogamous cichlid fish with biparental nest defence

In several animal taxa, genetic analyses have demonstrated that social monogamy and biparental brood care do not preclude polygamous reproduction. Few studies have been conducted in fish, but in fish species without alternative reproductive phenotypes, social monogamy was largely congruent with genetic parentage. In contrast to these findings, we report an exceptionally high level of multiple paternity in a socially monogamous cichlid fish with biparental nest defence ( Variabilichromis moorii ), inferred from microsatellite and mitochondrial data of 10 broods. Whereas all offspring in a nest shared a common mother, each brood was sired by 2 to > 10 males. None of the inferred sires was assigned a large proportion of the brood. Paternity was estimated as the minimum number of sires required to explain multilocus offspring genotypes, and as the maximum-likelihood number of sires given population allele frequencies. Analysis of simulated brood genotypes suggested that, although these two methods tend to under- and overestimate, respectively, the true number of sires, primary sires with many offspring in a brood would have been detected. Hence, the genetic data indicate that the nest tending males suffer substantial cuckoldry and provide alloparental care for a large number of unrelated fry. We have no data on the social status of the cuckolding males, but due to synchronous spawning of pairs and commitment to brood care of paired males, it is possible that most of the parasitic spawners are solitary males.