Biological rhythms in birds — development, insights and perspectives

The aim of this review is to show that probably the internal clock of precocial birds is imprinted in the prenatal period by exogenous factors (zeitgeber). The activity of organ functions occurs early during embryonic development, before this function is ultimately necessary to ensure the survival of the embryo. Prenatal activation of some functional systems may have a training effect on the postnatal efficiency.The development of physiological control systems is influenced by endogenous and exogenous factors during the late prenatal and early postnatal period: epigenetic adaptation processes play an important role in the development of animals; they have acquired characteristics which are innated but not genetically fixed. As a rule, the actual value during the determination period has a very strong influence on the set-point of the system. This will be explained using the example of thermoregulation.It is shown in detail that it seems to be possible to imprint the prenatal development of circadian rhythms by periodic changes of the light-dark cycle but not by rhythmic influence of acoustic signals.Altogether, there are more questions open than solved concerning the perinatal genesis of circadian rhythms in birds. Topics are given for the future research.     

Distribution of chloroplast DNA diversity within and among populations in gynodioecious Beta vulgaris ssp. maritima (Chenopodiaceae)

With the recent technical advances in molecular biology, chloroplast DNA (cpDNA) has become a marker used for the study of cytoplasmic differentiation of natural populations of plants. As chloroplasts are maternally inherited in most plant species, the seed component of gene flow is thus made accessible. We present here a study of cpDNA polymorphism within the maritima subspecies of the gynodioecious Beta vulgaris in which we try to assess the impact of such a reproductive system on seed flow. One hundred and eighty-eight wild beets were sampled from 20 hermaphroditic and 20 gynodioecious (i.e. containing both hermaphroditic and female plants) populations from the Atlantic coast of Europe. cpDNA variability in these populations was characterized with a rapid restriction fragment length polymorphism (RFLP) method. Eight cpDNA haplotypes were found. Strong differentiation among populations was observed ( F _ST = 0.43) and was consistent with isolation by distance, although most of the cpDNA haplotypes were ubiquitous. Gynodioecy seems to affect the distribution of cpDNA diversity: gynodioecious populations of Beta vulgaris ssp. maritima contained a greater number of cpDNA types but were less differentiated among themselves than hermaphroditic ones.     

In and out: Effects of shoot- vs. rooted-presence sampling methods on plant diversity measures in mountain grasslands

Plant diversity measures (e.g., alpha- and beta-diversity) provide the basis for a number of ecological indication and monitoring methods. These measures are based on species counts in sampling units (plots or quadrats). However, there are two alternative conventions for defining a vascular plant species as “present” in a plot, i.e. “shoot presence” (a species is recorded if the vertical projection of any above-ground part falls within the plot) and “rooted presence” (a species is recorded only when an individual is rooted inside the plot). Very few studies addressed the effects of the two sampling conventions on species richness and diversity indices. We sampled mountain dry grasslands in Italy across different plot sizes and vegetation types to assess how large is the difference in alpha- and beta-diversity values and in sample-based rarefaction curves between the two methods. We found that the difference is greatly dependent on plot size, being more relevant, both in absolute and percentage values, at smaller grain; it is also dependent on habitat type, being larger in shallow-soil communities, as they have a sparser vegetation structure and host life-form types with a larger lateral spread. At fine spatial scales (<1 m²) the difference is large enough to bias statistical inference, and we conclude that at such scales one should not attempt to compare plant diversity indices if they were not obtained with the same sampling convention.     

Genetic analysis of seven Italian horse breeds based on mitochondrial DNA D‐loop variation

To understand the origin and genetic diversity of Italian horses, mitochondrial DNA D‐loop sequences were generated for 163 horses from seven breeds. Sequence analysis of a 480‐bp segment revealed a total of 84 haplotypes with 57 polymorphic sites, indicating multiple maternal origins and high genetic diversity. Comparison of the haplotypes with the equine mtDNA haplotype/haplogroup nomenclature showed a haplogroup distribution in the Italian breeds more similar to that found in the Middle East breeds than in the European breeds, probably due to the economic and cultural relationship with the Middle East in the past centuries.     

Intra- and interspecific tree diversity promotes multitrophic plant–Hemiptera–ant interactions in a forest diversity experiment

Interactions between species of different trophic levels have long been recognized as fundamental processes in ecology. Although mounting evidence indicates that plant species diversity (PSD) or plant genetic diversity (PGD) can influence the plant-associated arthropod community, these two fundamental levels of biodiversity are not often manipulated simultaneously to assess their effects on species interactions. We used a large tree diversity experiment (BEF-China), which manipulates PSD and PGD in a crossed design to test individual and combined effects of PSD and PGD on multitrophic interaction networks and interaction partner species richness and occurrence. We focused on two tree species, on which sap-sucking Hemiptera and interacting ant species commonly occur. This tri-trophic interaction can be divided into the antagonistic plant–Hemiptera interaction and the mutualistic Hemiptera–ant interaction, known as trophobioses. Qualitative evaluation of tri-trophic interaction networks at different PSD and PGD combinations showed increased interaction partner redundancy at high PSD and PGD. This was supported by increased Hemiptera species richness at high PSD and PGD. Furthermore, the data indicate higher occurrence of Hemiptera and trophobioses and higher trophobiotic ant species richness with increasing PSD and PGD. As no plant diversity component alone caused an effect we conclude that the combined effect of high PGD and high PSD might be additive. In summary, as plant genetic diversity, especially at low species richness, seems to increase the interaction partner redundancy in interaction networks and the diversity of interacting communities, we suggest that genetic diversity should be considered in forest conservation and restoration programs.