Local-Scale Patterns of Genetic Variability, Outcrossing, and Spatial Structure in Natural Stands of Arabidopsis thaliana

As Arabidopsis thaliana is increasingly employed in evolutionary and ecological studies, it is essential to understand patterns of natural genetic variation and the forces that shape them. Previous work focusing mostly on global and regional scales has demonstrated the importance of historical events such as long-distance migration and colonization. Far less is known about the role of contemporary factors or environmental heterogeneity in generating diversity patterns at local scales. We sampled 1,005 individuals from 77 closely spaced stands in diverse settings around Tübingen, Germany. A set of 436 SNP markers was used to characterize genome-wide patterns of relatedness and recombination. Neighboring genotypes often shared mosaic blocks of alternating marker identity and divergence. We detected recent outcrossing as well as stretches of residual heterozygosity in largely homozygous recombinants. As has been observed for several other selfing species, there was considerable heterogeneity among sites in diversity and outcrossing, with rural stands exhibiting greater diversity and heterozygosity than urban stands. Fine-scale spatial structure was evident as well. Within stands, spatial structure correlated negatively with observed heterozygosity, suggesting that the high homozygosity of natural A. thaliana may be partially attributable to nearest-neighbor mating of related individuals. The large number of markers and extensive local sampling employed here afforded unusual power to characterize local genetic patterns. Contemporary processes such as ongoing outcrossing play an important role in determining distribution of genetic diversity at this scale. Local “outcrossing hotspots” appear to reshuffle genetic information at surprising rates, while other stands contribute comparatively little. Our findings have important implications for sampling and interpreting diversity among A. thaliana accessions

Anatomical Specializations for Nocturnality in a Critically Endangered Parrot, the Kakapo (Strigops habroptilus)

The shift from a diurnal to nocturnal lifestyle in vertebrates is generally associated with either enhanced visual sensitivity or a decreased reliance on vision. Within birds, most studies have focused on differences in the visual system across all birds with respect to nocturnality-diurnality. The critically endangered Kakapo (Strigops habroptilus), a parrot endemic to New Zealand, is an example of a species that has evolved a nocturnal lifestyle in an otherwise diurnal lineage, but nothing is known about its' visual system. Here, we provide a detailed morphological analysis of the orbits, brain, eye, and retina of the Kakapo and comparisons with other birds. Morphometric analyses revealed that the Kakapo's orbits are significantly more convergent than other parrots, suggesting an increased binocular overlap in the visual field. The Kakapo exhibits an eye shape that is consistent with other nocturnal birds, including owls and nightjars, but is also within the range of the diurnal parrots. With respect to the brain, the Kakapo has a significantly smaller optic nerve and tectofugal visual pathway. Specifically, the optic tectum, nucleus rotundus and entopallium were significantly reduced in relative size compared to other parrots. There was no apparent reduction to the thalamofugal visual pathway. Finally, the retinal morphology of the Kakapo is similar to that of both diurnal and nocturnal birds, suggesting a retina that is specialised for a crepuscular niche. Overall, this suggests that the Kakapo has enhanced light sensitivity, poor visual acuity and a larger binocular field than other parrots. We conclude that the Kakapo possesses a visual system unlike that of either strictly nocturnal or diurnal birds and therefore does not adhere to the traditional view of the evolution of nocturnality in birds

Tiny hitchhikers and parasites: a review of Australian heterostigmatic mites (Acari: Prostigmata) associated with insects, with description of three new species

Heterostigmatic mites (Heterostigmata) are highly diverse, have symbiotic associations with various insects and occur worldwide. Despite Australia's rich insect biodiversity, little is known about its heterostigmatic mites. In this study, we conducted a preliminary study on heterostigmatic mites associated with beetles in eastern Australia and found four species, of which three were new: Caraboacarus stammeri Krczal, 1959 (Caraboacaridae) and Eutarsopolipus orpheus Katlav & Seeman, sp. nov., (Podapolipidae) associated with Australian-endemic Gnathaphanus melbournensis (Castelnau, 1867) (Carabidae); Hoplocheylus australiensis Katlav & Seeman, sp. nov., (Tarsocheylidae) phoretic on Australian-endemic Mastachilus quaestionis (Kuwert, 1891) (Passalidae); and Pavania gazellatris Katlav & Seeman, sp. nov., (Dolichocybidae) phoretic on introduced Digitonthophagus gazella (Fabricius, 1787) (Scarabaeidae). The species of Caraboacaridae, Dolichocybidae and Tarsocheylidae are the first species records of these families in Australia. It is likely that two of the three new species are Australian endemics, while P. gazellatris may be a more recent arrival on introduced dung beetles, possibly arriving with imports of exotic adult dung beetles. Furthermore, we provide an overview of the heterostigmatic mite fauna of Australia that consists of less than 90 species belonging to 13 families, with representatives of all known seven superfamilies. These mites have so far been mostly reported on beetles but also on other insect orders (Blattodea, Diptera, Hemiptera, Hymenoptera, Orthoptera, Thysanoptera). Our findings of three new species and one new record based on the analysis of a relatively small number of specimens and beetle species suggest that more comprehensive studies of host insect taxa will reveal a substantially larger Australian diversity of heterostigmatic mites

The use of combined lateral and medial releases in the treatment of post-traumatic contracture of the elbow

Elbow stiffness is a common disorder, which restricts daily activities. Between 30° and 130° of elbow movement is usually enough to perform most daily activities. However, a 10° to 15° loss of elbow extension may be a problem when the patient is an athlete. From 1996 to 2004, 20 elbows of 20 patients (who were available for follow-up examination) were treated by lateral and medial release at Kocaeli University, for post-traumatic elbow contracture. Preoperative and the postoperative 12-month follow-up measurements were performed. The mean preoperative arc of motion was 35° and this value improved to 86.2°. The maximum improvement at the arc of motion was 105°. In an effort to understand the pathophysiology of the condition, surgical approaches may be used safely. The purpose of this study was to assess the functional outcome of the elbow joint after using a combination of lateral and medial approaches to treat elbow stiffness