Supernumerary chromosomes in Tradescantia I. Meiotic behavior of three homologous isochromosomes

The meiotic behavior of three homologous iso-supernumerary chromosomes in an individual of Tradescantia ohiensis Raf. has revealed sevealed several interesting features. There is a high frequency of pairing-partner exchange within bivalents and trivalents. The mean chiasma frequency per chromosome is relatively high (1.046) for supernumerary chromosomes and is not significantly different from that of the much larger normal (A) chromosomes. The high frequency of trivalent and bivalent configurations would seem to suggest that the isosupernumerary chromosomes are premeiotically dispositioned to allow for full random pairing among all six homologous arms.     

Mitochondrial DNA analysis reveals genetic structure in two New Zealand Cook’s petrel (<Emphasis Type="Italic">Pterodroma cookii</Emphasis>) populations

The endangered Cook’s petrel (Pterodroma cookii) is restricted to two separated populations at the extremes of its former range across New Zealand. Prior work revealed morphological, foraging, and reproductive isolation between these two remnant populations. To aid the conservation management of the species, additional information is required on the genetic structure of Cook’s petrel. We used mitochondrial DNA sequences (Cytochrome Oxidase subunit 1 gene), collected from 26 and 19 Cook’s petrel breeding on Little Barrier Island (LBI) and Codfish Island (CDF), respectively, for this preliminary study. We uncovered distinct population genetic structure with analysis of molecular variance suggesting genetic isolation of the populations. Levels of genetic variation were higher in the LBI population (four haplotypes present; h = 0.34 and π = 0.10) whereas the CDF population had only one haplotype that was distinct from the LBI population. Our results indicate that Cook’s petrel constitute two distinct management units for which conservation of genetic as well as behavioural and morphological diversity should be a priority. Further genetic studies using nuclear markers are recommended.     

Molecular tracking of individual host use in the Shiny Cowbird – a generalist brood parasite

Generalist parasites exploit multiple host species at the population level, but the individual parasite's strategy may be either itself a generalist or a specialist pattern of host species use. Here, we studied the relationship between host availability and host use in the individual parasitism patterns of the Shiny Cowbird Molothrus bonariensis, a generalist avian obligate brood parasite that parasitizes an extreme range of hosts. Using five microsatellite markers and an 1120‐bp fragment of the mtDNA control region, we reconstructed full‐sibling groups from 359 cowbird eggs and chicks found in nests of the two most frequent hosts in our study area, the Chalk‐browed Mockingbird Mimus saturninus and the House Wren Troglodytes aedon. We were able to infer the laying behavior of 17 different females a posteriori and found that they were mostly faithful to a particular laying area and host species along the entire reproductive season and did not avoid using previously parasitized nests (multiple parasitism) even when other nests were available for parasitism. Moreover, we found females using the same host nest more than once (repeated parasitism), which had not been previously reported for this species. We also found few females parasitizing more than one host species. The use of an alternative host was not related to the main hosts' nest availability. Overall, female shiny cowbirds use a spatially structured and host species specific approach for parasitism, but they do so nonexclusively, resulting in both detectable levels of multiple parasitism and generalism at the level of individual parasites.     

Individual patterns of habitat and nest-site use by hosts promote transgenerational transmission of avian brood parasitism status

Brood parasitic birds impose variable fitness costs upon their hosts by causing the partial or complete loss of the hosts' own brood. Growing evidence from multiple avian host-parasite taxa indicates that exposure of individual hosts to parasitism is not necessarily random and varies with habitat use, nest-site selection, age or other phenotypic attributes. For instance, nonrandom patterns of brood parasitism had similar evolutionary consequences to those of limited horizontal transmission of parasites and pathogens across space and time and altered the dynamics of both population productivity and co-evolutionary interactions of hosts and parasites. We report that brood parasitism status of hosts of brown-headed cowbirds Molothrus ater is also transmitted across generations in individually colour-banded female prothonotary warblers Protonotaria citrea. Warbler daughters were more likely to share their mothers' parasitism status when showing natal philopatry at the scale of habitat patch. Females never bred in their natal nestboxes but daughters of parasitized mothers had shorter natal dispersal distances than daughters of nonparasitized mothers. Daughters of parasitized mothers were more likely to use nestboxes that had been parasitized by cowbirds in both the previous and current years. Although difficult to document in avian systems, different propensities of vertical transmission of parasitism status within host lineages will have critical implications both for the evolution of parasite tolerance in hosts and, if found to be mediated by lineages of parasites themselves, for the difference in virulence between such extremes as the nestmate-tolerant and nestmate-eliminator strategies of different avian brood parasite species.     

Greater opportunities for sexual selection in male than in female obligate brood parasitic birds

Females are expected to have evolved to be more discriminatory in mate choice than males as a result of greater reproductive investment into larger gametes (eggs vs. sperm). In turn, males are predicted to be more promiscuous than females, showing both a larger variance in the number of mates and a greater increase in reproductive success with more mates, yielding more intense sexual selection on males vs. females (Bateman's Paradigm). However, sex differences in costly parental care strategies can either reinforce or counteract the initial asymmetry in reproductive investment, which may be one cause for some studies failing to conform with predictions of Bateman's Paradigm. For example, in many bird species with small female‐biased initial investment but extensive biparental care, both sexes should be subject to similar strengths of sexual selection because males and females are similarly restricted in their ability to pursue additional mates. Unlike 99% of avian species, however, obligate brood parasitic birds lack any parental care in either sex, predicting a conformation to Bateman's Paradigm. Here we use microsatellite genotyping to demonstrate that in brood parasitic brown‐headed cowbirds (Molothrus ater), per capita annual reproductive success increases with the number of mates in males, but not in females. Furthermore, also as predicted, the variance of the number of mates and offspring is greater in males than in females. Thus, contrary to previous findings in this species, our results conform to predictions of the Bateman's Paradigm for taxa without parental care.     

Merging ancient and modern DNA: extinct seabird taxon rediscovered in the North Tasman Sea

Ancient DNA has revolutionized the way in which evolutionary biologists research both extinct and extant taxa, from the inference of evolutionary history to the resolution of taxonomy. Here, we present, to our knowledge, the first study to report the rediscovery of an ‘extinct’ avian taxon, the Tasman booby (Sula tasmani), using classical palaeontological data combined with ancient and modern DNA data. Contrary to earlier work, we show an overlap in size between fossil and modern birds in the North Tasman Sea (classified currently as S. tasmani and Sula dactylatra fullagari, respectively). In addition, we show that Holocene fossil birds have mitochondrial control region sequences that are identical to those found in modern birds. These results indicate that the Tasman booby is not an extinct taxon: S. dactylatra fullagari O''Brien & Davies, 1990 is therefore a junior synonym of Sula tasmani van Tets, Meredith, Fullagar & Davidson, 1988 and all North Tasman Sea boobies should be known as S. d. tasmani. In addition to reporting the rediscovery of an extinct avian taxon, our study highlights the need for researchers to be cognizant of multidisciplinary approaches to understanding taxonomy and past biodiversity.     

Alarm responses are maintained during captive rearing in chicks of endangered kaki

The maintenance of species-specific behavioural repertoires and traditions is an important but often implicit goal of conservation efforts. When captive rearing is used as a conservation practice, it becomes critical to address its possible implications for the social and behavioural traits of developing individuals. In particular, animals must retain or acquire many of their behavioural abilities to increase the likelihood of survival upon release into the wild. This study investigated the behavioural development of critically endangered kaki (black stilt: Himantopus novaezelandiae ) chicks reared without live adult conspecifics. The captive rearing programme included playbacks of adult kaki alarm calls during cleaning and handling of precocial chicks housed as groups. We used videotaped observations and playback experiments to address the following questions: do kaki chicks respond differentially to (1) familiar versus unfamiliar adult kaki alarm calls and (2) conspecific alarm versus heterospecific control vocalizations. Adult-naïve kaki chicks exhibited a varied behavioural repertoire over their early development. In multivariate analyses, when age was statistically controlled, chicks showed responses to familiar and unfamiliar alarm calls that were similar in magnitude. In contrast, following conspecific alarm calls chicks had longer average latencies to resume pre-playback activities than following heterospecific vocalizations. Although the generality of these conclusions is limited by experimental constraints stemming from working with an endangered species, the findings suggest that current management techniques produce captive-reared kaki for release into the wild that possess many of the behavioural and auditory recognition skills that are required for survival.     

AUTOTETRAPLOIDY IN HAPLOPAPPUS SPINULOSUS HYBRIDS: EVIDENCE FROM NATURAL AND SYNTHETIC TETRAPLOIDS

Haplopappus spinulosus (Asteraceae) is a herbaceous, perennial weed common throughout the western Great Plains of North America and includes both diploid and tetraploid populations. A number of populations in southeastern Colorado were analyzed cytogenetically and morphologically for two reasons. First, initial observations during a routine population survey showed they were morphologically intermediate between the diploid subspecies glaberrimus and spinulosus, suggesting they might have arisen via hybridization. Second, cytological examination revealed that they were tetraploid. Because there was indication of hybrid origin, it was of interest to determine whether the populations were behaving as autopolyploids or segmental allopolyploids. The distinction between these two polyploid types is not easily made since both are likely to form multivalents at meiosis, but equations derived from a model proposed by Jackson and Hauber (1982) have made it possible to determine statistically whether a tetraploid individual is behaving meiotically as an autotetraploid. Meiotic configuration frequencies at diakinesis were determined for each tetraploid plant sampled, and observed frequencies were compared to those expected for an autotetraploid having the same maximum number of chiasmata per bivalent, chiasma frequency and chromosome number. In general, the meiotic behavior of the tetraploids was no different from that expected for autoploids. The initial hypothesis that the populations were derived from hybridization was tested by a detailed cytogenetic and morphological study of the presumed parental subspecies, F, hybrids, and natural putative hybrids. The evidence supports the hypothesis that the natural autotetraploids arose from the hybridization of ssp. glaberrimus and ssp. spinulosus.     

Size dimorphism and avian‐perceived sexual dichromatism in a New Zealand endemic bird,the whitehead Mohoua albicilla

Sex differences in behavior, morphology, and physiology are common in animals. In many bird species, differences in the feather colors of the sexes are apparent when judged by human observers and using physical measures of plumage reflectance, cryptic (to human) plumage dichromatism has also been detected in several additional avian lineages. However, it remains to be confirmed in almost all species whether sexual dichromatism is perceivable by individuals of the studied species. This latter step is essential because it allows the evaluation of alternative hypotheses regarding the signaling and communication functions of plumage variation. We applied perceptual modeling of the avian visual system for the first time to an endemic New Zealand bird to provide evidence of subtle but consistent sexual dichromatism in the whitehead, Mohoua albicilla. Molecular sexing techniques were also used in this species to confirm the extent of the sexual size dimorphism in plumage and body mass. Despite the small sample sizes, we now validate previous reports based on human perception that in male whiteheads head and chest feathers are physically brighter than in females. We further suggest that the extent of sexual plumage dichromatism is pronounced and can be perceived by these birds. In contrast, although sexual dimorphism was also detectable in the mass among the DNA‐sexed individuals, it was found to be less extensive than previously thought. Sexual size dimorphism and intraspecifically perceivable plumage dichromatism represent reliable traits that differ between female and male whiteheads. These traits, in turn, may contribute to honest communication displays within the complex social recognition systems of communally breeding whitehead and other group‐breeding taxa. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.