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We examined factors predicting female densities within the common home ranges of related females ("clans") in bushbuck Tragelaphus scriptus Pallas, 1776. In this species, each female forms an individual home range, but the home ranges of matrilineal clan members strongly overlap. We found female densities to increase in areas with high canopy cover. Moreover, individual home range sizes tended to decrease with increasing cover. Food plant availability and intruder pressure by two heterospecific competitors did not significantly affect female densities. Apparently, canopy cover is the major limited resource in this species. A possible explanation is that both adult bushbuck and - even more markedly - fawns hide from predators in dense vegetation, in particular in thicket clumps and coalescences. The study shows an effect of habitat properties (eg sufficient canopy cover) on a within-population level in bushbuck, where female densities differ even among proximate clan areas
For two sympatric species of African weakly electric fish, Campylomormyrus tamandua and Campylomormyrus numenius, we monitored ontogenetic differentiation in electric organ discharge (EOD) and established a molecular phylogeny, based on 2222 bp from cytochrome b, the S7 ribosomal protein gene, and four flanking regions of unlinked microsatellite loci. In C tamandua, there is one common EOD type, regardless of age and sex, whereas in C numenius we were able to identify three different male adult EOD waveform types, which emerged from a single common EOD observed in juveniles. Two of these EOD types formed well supported clades in our phylogenetic analysis. In an independent line of evidence, we were able to affirm the classification into three groups by microsatellite data. The correct assignment and the high pairwise FST values support our hypothesis that these groups are reproductively isolated. We propose that in C numenius there are cryptic species, hidden behind similar and, at least as juveniles, identical morphs.
More than one century ago, sturgeons were prevalent species in the fish communities of all major German rivers both in the North and the Baltic seas drainages. Since then, the populations declined rapidly due to river damming, overfishing and pollution. The last sturgeon catches in the Baltic drainage system occurred during the late 1960ies. Only a few individual captures have been reported during the last 30 years with the most recent records in the Lake Ladoga ( Russia), where the last confirmed catch was recorded in 1984, and a single individual caught off Estonia in 1996. Today, sturgeons are considered missing or extinct in German waters. First attempts for remediation of the species were undertaken in the mid 1990ies. Subsequently, phylogenetic and population genetic analyses of the species were carried out using mtDNA, microsatellites, and nuclear markers ( SNPs). These genetic analyses using recent and historic material have proven the existence of two different species in the Baltic Sea in what was previously considered to represent the European Atlantic sturgeon only. In the Baltic Sea, the American Atlantic sturgeon ( A. oxyrinchus) succeeded to colonize this brackish water system during the Middle Ages. In the North Sea, the European Atlantic sturgeon ( A. sturio) is considered to be the endemic species. These results led to the separation of the remediation activities in the North Sea and the Baltic Sea tributaries. Further studies on the mechanism that lead to the extinction of A. sturio in Germany and the subsequent succession of the A. oxyrinchus mtDNA haplotype are currently been carried out. Broodstock development using the northernmost populations of A. oxyrinchus is currently under way. As a further prerequisite to re-introduce this species into the Baltic, the evaluation of the status of critical habitats for the early life stages of the American Atlantic sturgeon in the River Odra has been performed in collaboration with the Institute for Inland Fisheries of Poland. Alternative fisheries techniques, based on the data of by-catch of exotic sturgeons in the fishery, are presently developed in close cooperation with the fishery to reduce fisheries related mortality in juvenile sturgeons upon release. Monitoring of habitat utilization and migration characteristics of juvenile fish upon experimental release will have to be carried out shortly, using acoustic telemetry, with the aim to follow the fate of the released fish and to determine the best time-size-release-window for future release programmes.
Males often face strong mating competition by neighboring males in their social environment. A recent study by Plath et al. (Anim Behav 75:21-29, 2008a) has demonstrated that the visual presence of a male competitor (i.e., an audience male) affects the expression of male mating preferences in a poeciliid fish (Poecilia mexicana) with a weaker expression of mating preferences when an audience male observed the focal male. This may be a tactic to reduce sperm competition, since surrounding males likely share intrinsic preferences for female traits or copy mate choice decisions. Here, we examined the hypothesis that a same-sex audience would affect female mate preferences less than male mating preferences. Our hypothesis was based on the assumptions that (1) competition for mates in a fashion that would be comparable in strength to sperm competition or overt male-male aggression is absent among Poecilia females, and (2) P. mexicana females typically form female-biased shoals, such that almost any female mate choice in nature occurs in front of a female audience. Poecilia females (P. mexicana, surface and cave form, and the closely related gynogenetic Poecilia formosa) were given a choice between a large and a small male, and the tests were repeated while a conspecific, a heterospecific, or no audience female (control) was presented. Females spent more time in the neutral zone and, thus, less time near the males during the second part of a trial when an audience was presented, but-consistent with predictions-females showed only slightly weaker expression of mate preferences during the second part of the tests. This decline was not specific to the treatment involving an audience and was significantly weaker than the effect seen in the male sex.
Orbiniid phylogeny is matter of debate and incongruence between hypothesis based on molecules and morphology has been repeatedly reported. Moreover, the phylogenetic position of the "oligochaetoid polychaetes" of the taxon Questa varies between morphological and molecular cladistic analyses. Here, we present a nearly complete mitochondrial genome of Questa ersei. The mitochondrial gene order is roughly identical to known orbiniid taxa. Several translocations of tRNAs are unique to Orbiniidae and Questa when compared to other annelid mitochondrial genomes. Additionally, we assembled sequence data of six genes (18S, 16S, cox1, cox3, nad1, nad4) for a representative orbiniid taxon sampling and analysed all data in concatenation using Maximum Likelihood and Bayesian inference. For comparison with morphology we compiled a morphological data matrix for all taxa included in our molecular analyses. Our results strongly support a close relationship of Questa with orbiniids (sequence data, gene order, an 18 bp indel, morphology), and a position nested within orbiniids is recovered in our sequence based analyses. We demonstrate remarkable incongruence of most included morphological characters with the recovered best ML tree and suppose that repeated independent character loss might be an explanation.
Using degenerate primers, we were able to identify seven Hox genes for the myzostomid Myzostoma cirriferum. The recovered fragments belong to anterior class (Mci_lab, Mci_pb), central class (Mci_Dfd, Mci_Lox5, Mci_Antp, Mci_Lox4), and posterior class (Mci_Post2) paralog groups. Orthology assignment was verified by phylogenetic analyses and presence of diagnostic regions in the homeodomain as well as flanking regions. The presence of Lox5, Lox4, and Post2 supports the inclusion of Myzostomida within Lophotrochozoa. We found signature residues within flanking regions of Lox5, which are also found in annelids, but not in Platyhelminthes. As such the available Hox genes data of myzostomids support an annelid relationship.
We analyzed mtDNA polymorphisms (parts of control region, ND5, ND2, Cytb, 12S, together 902 bp) in 59 scat and 18 tissue samples from 13 Indian populations of the critically endangered Indian tiger (Panthera tigris tigris), along with zoo animals as reference. Northern tiger populations exhibit two unique haplotypes suggesting genetic isolation. Western populations from Sariska (extinct in 2004) and Ranthambore are genetically similar, such that Ranthambore could serve as a source for reintroduction in Sariska. Zoo populations maintain mitochondrial lineages that are rare or absent in the wild.
It is well established that reproductive isolation often arises from genome incompatibilities and that genes encoding reproductive traits are less prone to introgression. Hybrid zones of Mytilus trossulus and Mytilus edulis provide an intriguing model to assess reproductive isolation. Although gene flow is restricted in North America, introgression is pervasive in the Baltic. This study aimed at analyzing the shape of multilocus clines across the Baltic contact zone between M. edulis and M. trossulus to infer mechanisms of restriction to gene flow. We use maximum likelihood methods to construct the best fitting individual clines for five markers located on biparentally inherited autosomes and paternally and maternally inherited mitochondrial DNA (mtDNA). Strong cline shape differences among markers suggest that reproductive isolation arising from genome-wide incompatibilities is weak, and that these discrepancies possibly result from genetic drift, hybrid zone movement or marker-specific selection. However, the finding of a common cline center for M7 lysin (involved in fertilization) and paternally transmitted mtDNA (causing nuclear-mitochondrial incompatibilities in hybrids) suggest that these loci may play a role in incomplete reproductive isolation.
Mate choice is mediated by a range of sensory cues, and assortative mating based on these cues can drive reproductive isolation among diverging populations. A specific feature of mormyrid fish, the electric organ discharge (EOD), is used for electrolocation and intraspecific communication. We hypothesized that the EOD also facilitates assortative mating and ultimately promotes prezygotic reproductive isolation in African weakly electric fishes. Our behavioural experiments using live males as well as EOD playback demonstrated that female mate recognition is influenced by EOD signals and that females are attracted to EOD characteristics of conspecific males. The dual function of the EOD for both foraging and social communication (including mate recognition leading to assortative mating) underlines the importance of electric signal differentiation for the divergence of African weakly electric fishes. Thus, the EOD provides an intriguing mechanism promoting trophic divergence and reproductive isolation between two closely related Campylomormyrus species occurring in sympatry in the lower Congo rapids.
Background: Phylogenomic analyses recently became popular to address questions about deep metazoan phylogeny. Ribosomal proteins (RP) dominate many of these analyses or are, in some cases, the only genes included. Despite initial hopes, hylogenomic analyses including tens to hundreds of genes still fail to robustly place many bilaterian taxa. Results: Using the phylogenetic position of myzostomids as an example, we show that phylogenies derived from RP genes and mitochondrial genes produce incongruent results. Whereas the former support a position within a clade of platyzoan taxa, mitochondrial data recovers an annelid affinity, which is strongly supported by the gene order data and is congruent with morphology. Using hypothesis testing, our RP data significantly rejects the annelids affinity, whereas a platyzoan relationship is significantly rejected by the mitochondrial data. Conclusion: We conclude (i) that reliance of a set of markers belonging to a single class of macromolecular complexes might bias the analysis, and (ii) that concatenation of all available data might introduce conflicting signal into phylogenetic analyses. We therefore strongly recommend testing for data incongruence in phylogenomic analyses. Furthermore, judging all available data, we consider the annelid affinity hypothesis more plausible than a possible platyzoan affinity for myzostomids, and suspect long branch attraction is influencing the RP data. However, this hypothesis needs further confirmation by future analyses.
Background: Multidirectional interactions in social networks can have a profound effect on mate choice behavior; e.g., Poecilia mexicana males show weaker expression of mating preferences when being observed by a rival. This may be an adaptation to reduce sperm competition risk, which arises because commonly preferred female phenotypes will receive attention also from surrounding males, and/or because other males can copy the focal male's mate choice. Do P. mexicana males indeed respond to perceived sperm competition risk? We gave males a choice between two females and repeated the tests under one of the following conditions: (1) an empty transparent cylinder was presented (control); (2) another ("audience") male inside the cylinder observed the focal male throughout the 2nd part, or (3) the audience male was presented only before the tests, but could not eavesdrop during the actual choice tests (non-specific sperm competition risk treatments); (4) the focal male could see a rival male interact sexually with the previously preferred, or (5) with the non-preferred female before the 2nd part of the tests (specific sperm competition risk treatments). Results: The strength of individual male preferences declined slightly also during the control treatment (1). However, this decrease was more than two-fold stronger in audience treatment (2), i.e., with non-specific sperm competition risk including the possibility for visual eavesdropping by the audience male. No audience effect was found in treatments (3) and (5), but a weak effect was also observed when the focal male had seen the previously preferred female sexually interact with a rival male (treatment 4; specific sperm competition risk). Conclusion: When comparing the two 'non-specific sperm competition risk' treatments, a very strong effect was found only when the audience male could actually observe the focal male during mate choice [treatment (2)]. This suggests that focal males indeed attempt to conceal their mating preferences so as to prevent surrounding males from copying their mate choice. When there is no potential for eavesdropping [treatment (3)], non-specific specific sperm competition risk seems to play a minor or no role. Our results also show that P. mexicana males tend to share their mating effort more equally among females when the resource value of their previously preferred mate decreases after mating with a rival male (perceived specific sperm competition risk), but this effect is comparatively weak.
Several recent studies reported on so-called audience effects in male Atlantic mollies (Poecilia mexicana), in which the visual presence of a potential rival affects male sexual activity. We asked whether and how audience effects interact with male sexual harassment. Poecilia mexicana almost constantly attempt to mate, while females are mostly non- responsive to male approaches. Females flee from this sexual harassment and, thus, are more vigilant in the presence of males, so females may have hampered feeding opportunities. Do audience effects lead to altered male sexual harassment? Focal females were given an opportunity to feed in the presence of a male or a female partner and the difference in feeding times was interpreted as an effect caused by male harassment. Tests were conducted without an audience (1), or an audience male was visually presented either directly inside the test tank (2), or further away (in an adjoining compartment (3)). We found that levels of pre-mating behaviour did not vary significantly among treatments, but males exhibited more copulation attempts (thrusting) in treatment (3), suggesting that males respond to increased risk of sperm competition with higher sperm expenditure. Females fed less (and started feeding later) when a harassing partner male was around, and this effect was not dependent on the audience treatment, but, overall, females spent more time feeding (and started feeding earlier) when an audience was presented. Hence, feeding time reductions appear to be independent of audience effects, but perceived 'safety in numbers' may lead to increased foraging in larger groups.
Investigating the dog genome we found 178965 introns with a moderate length of 200-1000 bp. A screening of these sequences against 23 different repeat libraries to find insertions of short interspersed elements (SINEs) detected 45276 SINEs. Virtually all of these SINEs (98%) belong to the tRNA-derived Can-SINE family. Can-SINEs arose about 55 million years ago before Carnivora split into two basal groups, the Caniformia (doglike carnivores) and the Feliformia (cat-like carnivores). Genome comparisons of dog and cat recovered 506 putatively informative SINE loci for caniformian phylogeny. In this study we show how to use such genome information of model organisms to research the phylogeny of related non-model species of interest. Investigating a dataset including representatives of all major caniformian lineages, we analysed 24 randomly chosen loci for 22 taxa. All loci were amplifiable and revealed 17 parsimony- informative SINE insertions. The screening for informative SINE insertions yields a large amount of sequence information, in particular of introns, which contain reliable phylogenetic information as well. A phylogenetic analysis of intron- and SINE sequence data provided a statistically robust phylogeny which is congruent with the absence/presence pattern of our SINE markers. This phylogeny strongly supports a sistergroup relationship of Musteloidea and Pinnipedia. Within Pinnipedia, we see strong support from bootstrapping and the presence of a SINE insertion for a sistergroup relationship of the walrus with the Otariidae.
The mussel Mytilus edulis can be used as model to study the molecular basis of reproductive isolation because this species maintains its species integrity, despite of hybridizing in zones of contact with the closely related species M. trossulus or M. galloprovincialis. This study uses selective antibody production by means of hybridoma technology to identify molecules which are involved in sperm function of M. edulis. Fragmented sperm were injected into mice and 25 hybridoma cell clones were established to obtain monoclonal antibodies (mAb). Five clones were identified producing mAb targeting molecules putatively involved in sperm function based on enzyme immunoassays, dot and Western blotting as well as immunostaining of tissue sections. Specific localization of these mAb targets on sperm and partly also in somatic tissue suggests that all five antibodies bind to different molecules. The targets of the mAb obtained from clone G26-AG8 were identified using mass spectrometry (nano-LC-ESI-MS/MS) as M6 and M7 lysin. These acrosomal proteins have egg vitelline lyses function and are highly similar (76%) which explains the cross reactivity of mAb G26- AG8. Furthermore, M7 lysin was recently shown to be under strong positive selection suggesting a role in interspecific reproductive isolation. This study shows that M6 and M7 lysin are not only found in the sperm acrosome but also in male somatic tissue of the mantle and the posterior adductor muscle, while being completely absent in females. The monoclonal antibody G26-AG8 described here will allow elucidating M7/M6 lysin function in somatic and gonad tissue of adult and developing animals.
Mountain gazelles (Gazella gazella) rank among the most critically endangered mammals on the Arabian Peninsula. Past conservation efforts have been plagued by confusion about the phylogenetic relationship among various 'phenotypically discernable' populations, and even the question of species boundaries was far from being certain. This lack of knowledge has had a direct impact on conservation measures, especially ex situ breeding programmes, hampering the assignment of captive stocks to potential conservation units. Here, we provide a phylogenetic framework, based on the analysis of mtDNA sequences (360 bp cytochrome b and 213 bp Control Region) of 126 individuals collected from the wild throughout the Arabian Peninsula and from captive stocks. Our analyses revealed two reciprocally monophyletic genetic lineages within the presumed species Gazella gazella: one 'northern clade' on the Golan Heights (Israel/Syrian border) and one genetically diverse larger clade from the rest of the Arabian Peninsula including the Arava Valley (Negev, Israel). Applying the Strict Phylogenetic Species Concept (sensu Mishler & Theriot, 2000) allows assigning species status to these two major clades.
In most mammals, females are philopatric while males disperse in order to avoid inbreeding. We investigated social structure in a solitary ungulate, the bushbuck Tragelaphus sylvaticus in Queen Elizabeth National Park, Uganda by combining behavioural and molecular data. We correlated spatial and social vicinity of individual females with a relatedness score obtained from mitochondrial DNA analysis. Presumed clan members shared the same haplotype, showed more socio-positive interactions and had a common home range. Males had a higher haplotype diversity than females. All this suggests the presence of a matrilineal structure in the study population. Moreover, we tested natal dispersal distances between male and female yearlings and used control region sequences to confirm that females remain in their natal breeding areas whereas males disperse. In microsatellite analysis, males showed a higher genetic variability than females. The impoverished genetic variability of females at both molecular marker sets is consistent with a philopatric and matrilineal structure, while the higher degree of genetic variability of males is congruent with a higher dispersal rate expected in this sex. Evidence even for male long-distance dispersal is brought about by one male carrying a haplotype of a different subspecies, previously not described to occur in this area.
Using molecular genetic methods and an ancient DNA approach, we studied population and species succession of rotifers of the genus Brachionus in the Kenyan alkaline-saline crater lake Sonachi since the beginning of the 19th century as well as distribution of Brachionus haplotypes in recent and historic sediments of other lakes of the East African Rift System. The sediment core record of Lake Sonachi displays haplotypes of a distinct evolutionary lineage in all increments. Populations were dominated by a single mitochondrial haplotype for a period of 150 years, and two putatively intraspecific turnovers in dominance occurred. Both changes are concordant with major environmental perturbations documented by a profound visible change in sediment composition of the core. The first change was very abrupt and occurred after the deposition of volcanic ash at the beginning of the 19th century. The second change coincides with a major lake level lowstand during the 1940s. It was preceded by a period of successively declining lake level, in which two other haplotypes appeared in the lake. One of these putatively belongs to another species documented in historical and recent Kenyan lake sediments. The analysis of plankton population dynamics through historical time can reveal patterns of population persistence and turnover in relation to environmental changes.
In this study, we have used fragments of three mitochondrial genes (Control Region, CR; transfer RNA for methionine, tRNA-Met; NADH dehydrogenase subunit 2, ND2 for a total of 1066 bp) to reconstruct the phylogeographic history of the endemic Philippine bulbul (Hypsipetes philippinus) at the scale of the central area of the Philippine archipelago. The study includes two of the five recognized subspecies (guimarasensis and mindorensis), 7 populations and 58 individuals. Multiple phylogenetic and network analyses support the existence of two reciprocally monophyletic maternal lineages corresponding to the two named subspecies. Molecular clock estimates indicate that the split between the two subspecies is consistent with the Pleistocene geological history of the archipelago. Patterns of relationships within guimarasensis are biogeographically less clear. Here, a combination of vicariance and dispersal needs to be invoked to reconcile the molecular data with the geographical origin of samples. In particular, the two islands Boracay and Negros host mitochondrial lineages that do not form monophyletic clusters. Our genetic data suggest multiple independent colonization events for these locations.
The development of rise Cenozoic East African Rift System (EARS) profoundly re-shaped the landscape and significantly increased the amplitude of short-term environmental response to climate variation. In particular, the development of amplifier lakes in rift basins after three million years ago significantly contributed to this exceptional sensitivity of East Africa to climate change compared to elsewhere on the African continent. Amplifier lakes are characterized by tectonically-formed graben morphologies in combination with an extreme contrast between high precipitation in the elevated parts of the catchment and high evaporation in the lake area. Such amplifier lakes respond rapidly to moderate, precessional-forced climate shifts, and as they do so apply dramatic environmental pressure to the biosphere. Rift basins, when either extremely dry or lake-filled, form important barriers for migration, mixing and competition of different populations of animals and hominins. Amplifier lakes link long-term, high-amplitude tectonic processes and short-term environmental fluctuations. East Africa may have become the place where early humans evolved as a consequence of this strong link between different time scales. (C) 2010 Elsevier Ltd. All rights reserved.
Background: Although nowaday it is broadly accepted that mitochondrial DNA (mtDNA) may undergo recombination, the frequency of such recombination remains controversial. Its estimation is not straightforward, as recombination under homoplasmy (i.e., among identical mt genomes) is likely to be overlooked. In species with tandem duplications of large mtDNA fragments the detection of recombination can be facilitated, as it can lead to gene conversion among duplicates. Although the mechanisms for concerted evolution in mtDNA are not fully understood yet, recombination rates have been estimated from "one per speciation event" down to 850 years or even "during every replication cycle".
Results: Here we present the first complete mt genome of the avian family Bucerotidae, i.e., that of two Philippine hornbills, Aceros waldeni and Penelopides panini. The mt genomes are characterized by a tandemly duplicated region encompassing part of cytochrome b, 3 tRNAs, NADH6, and the control region. The duplicated fragments are identical to each other except for a short section in domain I and for the length of repeat motifs in domain III of the control region. Due to the heteroplasmy with regard to the number of these repeat motifs, there is some size variation in both genomes; with around 21,657 bp (A. waldeni) and 22,737 bp (P. panini), they significantly exceed the hitherto longest known avian mt genomes, that of the albatrosses. We discovered concerted evolution between the duplicated fragments within individuals. The existence of differences between individuals in coding genes as well as in the control region, which are maintained between duplicates, indicates that recombination apparently occurs frequently, i. e., in every generation.
Conclusions: The homogenised duplicates are interspersed by a short fragment which shows no sign of recombination. We hypothesize that this region corresponds to the so-called Replication Fork Barrier (RFB), which has been described from the chicken mitochondrial genome. As this RFB is supposed to halt replication, it offers a potential mechanistic explanation for frequent recombination in mitochondrial genomes.