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Maternal responsiveness in adult hens was measured by studying their rates of vocalization over a period of 12 days. Four roups of hens were compared: one group was isolated both visually and tactually from chicks; two other groups were exposed either to visual cues or to tactile cues originating from chicks, and in the last group, hens received both types of cues. Visual or tactile cues alone induced similar levels of maternal responsiveness but simultaneous presentation of both types of cues induced maximum responsiveness.

Genetic studies of modern populations are raising many interesting questions about how far the modern gene pool is owed to incoming populations during the agricultural revolution in Neolithic Europe. But, as the authors show, studies of isotopic data from cemeteries reveal a picture of increasing subtlety at local level. While early farmers may have been initially newcomers in the upper Rhine they may also have soon intermarried with contemporary hunter-gatherers in the uplands. Keywords: European Neolithic agriculture, demography, stable isotope analysis, Studies of how agriculture spread from the Near East into Central Europe (ca. 7000 - 5000 BC) are essential to theories explaining the origins of the languages, genes and demography [...]

The impact of the various different natural and anthropogenic determinants on the genetic structure of the largest remaining population of the endangered golden-brown mouse lemur, Microcebus ravelobensis in Madagascar is discussed. The landscape characteristics are shown to exhibit an extremely significant role in the functional connectivity of different sites.

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When populations are separated for long periods and then brought into contact for a brief episode in part of their range, this can result in genetic admixture. To analyze this type of event we considered a simple model under which two parental populations ([P.sub.1] and [P.sub.2]) mix and create a hybrid population (H). After that event, the three populations evolve under pure drift without exchange during T generations. We developed a new method, which allows the simultaneous estimation of the time since the admixture event (scaled by the population size [t.sub.i] = T/[N.sub.i], where [N.sub.i] is the effective population size of population i) and the contribution of one of two parental populations (which we call [p.sub.1]). This method takes into account drift since the admixture event, variation caused by sampling, and uncertainty in the estimation of the ancestral allele frequencies. The method is tested on simulated data sets and then applied to a human data set. We find that (i) for single-locus data, point estimates are poor indicators of the real admixture proportions even when there are many alleles; (ii) biallelic loci provide little information about the admixture proportion and the time since admixture, even for very small amounts of drift, but can be powerful when many loci are used; (iii) the precision of the parameters' estimates increases with sample size (n = 50 vs. n = 200) but this effect is larger for the [t.sub.i]'s than for [p.sub.1]; and (iv) the increase in precision provided by multiple loci is quite large, even when there is substantial drift (we found, for instance, that it is preferable to use five loci than one locus, even when drift is 100 times larger for the five loci). Our analysis of a previously studied human data set illustrates that the joint estimation of drift and [p.sub.1] can provide additional insights into the data.

Author(s): Lounès Chikhi [1] Sir As a French postdoc currently living in England, I would like to comment on your News Feature on this topic, 'Young, gifted... and spurned' (Nature [...]

Humans have introduced plants and animals into new continents and islands with negative effects on local species. This has been the case of the olive that was introduced in Australia, New Zealand and Pacific islands where it became invasive. Two subspecies were introduced in Australia, and each successfully invaded a specific area: the African olive in New South Wales (NSW) and the Mediterranean olive in South Australia. Here, we examine their origins and spread and analyse a large sample of native and invasive accessions with chloroplast and nuclear microsatellites. African olive populations from the invaded range exhibit two South African chlorotypes hence supporting an introduction from South Africa, while populations from South Australia exhibit chlorotypes of Mediterranean cultivars. Congruently, nuclear markers support the occurrence of two lineages in Australia but demonstrate that admixture took place, attesting that they hybridized early after introduction. Furthermore, using an approximate Bayesian computation framework, we found strong support for the serial introduction of the African olive from South Africa to NSW and then from NSW to Hawaii. The taxon experienced successive bottlenecks that did not preclude invasion, meaning that rapid decisions need to be taken to avoid naturalization where it has not established a large population yet. [ABSTRACT FROM AUTHOR]

Examines complications and challenges in the study of human genetic history. Discussion on the complexity of human migration and demographic history; Importance of population structure in medical genetics; Description of inferential approaches available for interpreting human genetic variations.

Christoph Schwitzer, Lounes Chikhi, Giuseppe Donati et al. respond to a letter to the editor submitted in response to their article "Averting Lemur Extinctions Amid Madagascar's Political Crisis", which appeared in the February 21, 2014 issue of the journal.