Molecules,morphology and Mimeoma scarabs: evolutionary and taxonomic implications for a palm‐associated scarab group

Cyclocephaline scarabs, the second largest tribe of rhinoceros beetles, are important pollinators of early‐diverging angiosperm families in the tropics. The evolutionary history of cyclocephaline genera is poorly resolved and several genera are thought to be nonmonophyletic. We assess the monophyly of Mimeoma Casey, a group of Neotropical palm‐feeding scarabs, and its relationship to Cyclocephala with a phylogenetic analysis of 2899 bp of DNA sequence data and 18 morphological characters. All five species of Mimeoma were included in analyses along with species of Cyclocephala Dejean, Dyscinetus Harold and Tomarus Erichson as outgroup taxa. Nearly complete 28S, 12S and CO1 data were collected from 26 of 29 specimens, of which 16 samples were pinned, museum specimens. 28S data strongly support a nonmonophyletic Mimeoma; mitochondrial data (CO1 and 12S) suggest that Mimeoma species are nested within an apical clade of other Cyclocephala species; combined molecular and morphological data identify two strongly supported clades of Mimeoma species but do not support their sister relationship. Combined data show that Mimeoma species are nested within Cyclocephala, thus rendering Cyclocephala paraphyletic. Mimeoma is synonymized within Cyclocephala resulting in the following new combinations: Cyclocephala acuta Arrow n.comb ., Cyclocephala englemani (Ratcliffe) n.comb ., Cyclocephala maculata Burmeister n.comb ., Cyclocephala nigra (Endrödi) n.comb . and Cyclocephala signatoides Höhne n.comb . Our results demonstrate that pinned, museum specimens can be used to obtain DNA sequence data (particularly high‐copy gene regions) for evolutionary studies, and provide the first empirical support that host‐plant associations within cyclocephaline scarab clades are conserved at the plant family‐level.     

Migration distance rather than migration rate explains genetic diversity in human patrilocal groups

In patrilocal groups, females preferentially move to join their mate’s paternal relatives. The gender‐biased gene flow generated by this cultural practice is expected to affect genetic diversity across human populations. Greater female than male migration is predicted to result in a larger decrease in between‐group differentiation for mitochondrial DNA (mtDNA) than for the non‐recombining part of the Y chromosome (NRY). We address the question of how patrilocality affects the distribution of genetic variation in human populations controlling for confounding factors such as ethno‐linguistic heterogeneity and geographic distance which possibly explain the contradictory results observed in previous studies. By combining genetic and bio‐demographic data from Lesotho and Spain, we show that preferential female migration over short distances appears to minimize the impact of a generally higher female migration rate in patrilocal communities, suggesting patrilocality might influence genetic variation only at short ranges.     

Description and relationships of a new brackish-water snail genus (Gastropoda: Hydrobiidae: Littoridininae) from Hispaniola

Whole-animal anatomy is used in a cladistic analysis of five genera of brackish-water hydrobiids living in the western Atlantic. Antillobia margalefi gen. & sp. nov. (Hydrobiidae: Littoridininae) is described based on specimens from Lago Enriquillo, an inland saline lake in the Dominican Republic. The topology ( Hydrobia ( Spurwinkia ( Heleobia ( Heleobops ( Antillobia ))))) is considerably better than any alternative. Among 27 characters and a total of 39 character states used in the analysis, only two convergences are detected, and these involve the genitalia. Detailed anatomical data are shown to be necessary to assess relationships in the presence of constraints on morphological evolution imposed by a very small size.     

Seasonal dynamics of the brown dog tick,Rhipicephalus sanguineus,on a confined dog population in Italy

This study evaluated the seasonal dynamics of Rhipicephalus sanguineus (Latreille) (Acari: Ixodidae) on naturally infested dogs in a private shelter in southern Italy. From March to May 2008, 39 autochthonous mixed‐breed young dogs and 10 beagles were enrolled in the study. From March 2008 until March 2009, every 21 ± 2 days, 11 body sites of each dog were checked for ticks. At each follow‐up, the number of ticks, their developmental stage, sex and location on the dog's body were recorded. Adult ticks were found throughout the year, but immatures were absent in January and February. The adult tick population increased from July to August, whereas the load of immatures increased in early July and peaked in September, which suggests that R. sanguineus develops one generation per year in this area. The mean number of immature ticks per infested dog was higher than that of adults from March to October 2008. Ears, interdigital areas and armpits were the most frequent attachment sites of adult ticks. At the last follow‐up, a total of 2266 ticks were collected and identified as R. sanguineus. The results suggest that R. sanguineus develops one generation per year in the study area, but that it infests dogs in all seasons. This information should be taken into account when planning control programmes against this tick species and the pathogens it transmits.     

The effect of ozone on the emission of carbonyls from leaves of adult Fagus sylvatica

Under the site conditions of a temperate forest, the exchange of short-chained oxygenated carbonyls (aldehydes, ketones) was assessed from leaves of adult European beech trees. The crowns of the trees were either exposed to an elevated O₃ regime as released by a free-air fumigation system (2 × O₃) or to the unchanged O₃ regime at the site (1 × O₃, ‘control’). Daily fluctuations of oxygenated carbonyls were quantified in relation to environmental and physiological factors. In particular, the effect of O₃ on carbonyl exchange was studied. Measurements of leaf gas exchange were performed with a dynamic cuvette system, and carbonyl fluxes were determined using 2,4-dinitrophenylhydrazine (DNPH)-coated silica gel cartridges. Leaves mainly emitted acetaldehyde, formaldehyde and acetone. Acetaldehyde dominated the emissions, amounting up to 100 nmol m⁻² min⁻¹, followed by formaldehyde (approximately 80 nmol m⁻² min⁻¹) and acetone (approximately 60 nmol m⁻² min⁻¹). Carbonyl emissions were highest during midday and significantly lowered at night, irrespective of the O₃ exposure regime. Trees exposed to 2 × O₃ emitted acetaldehyde and acetone at enhanced rates. The findings are of particular significance for future climate change scenarios that assume increased O₃ levels.     

Phylogenetic relationships of the pygmy rice rats of the genus Oligoryzomys Bangs, 1900 (Rodentia: Sigmodontinae)

Sequences from two mitochondrial genes (cytochrome b and NADH1) were used to produce a molecular phylogeny for 12 named and two undescribed species of the genus Oligoryzomys. All analyses placed Oligoryzomys microtis as the most basal taxon, a finding consistent with previous studies that suggested the west‐central Amazon as a centre of origin for the tribe Oryzomyini to which Oligoryzomys belongs. Biogeographically, this suggests that Oligoryzomys had a South American origin, and later advanced northwards, entering Central America and Mexico more recently. Different analyses have provided consistent support for several additional clades that did not necessarily agree with the species groups hypothesized by previous studies. A molecular clock derived for these data suggests an origin for the genus of 6.67 Mya, with most speciation within the genus occurring between 3.7 and 1.5 Mya. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 160 , 551–566.     

Isoprene synthesis protects transgenic tobacco plants from oxidative stress

Isoprene emission represents a significant loss of carbon to those plant species that synthesize this highly volatile and reactive compound. As a tool for studying the role of isoprene in plant physiology and biochemistry, we developed transgenic tobacco plants capable of emitting isoprene in a similar manner to and at rates comparable to a naturally emitting species. Thermotolerance of photosynthesis against transient high-temperature episodes could only be observed in lines emitting high levels of isoprene; the effect was very mild and could only be identified over repetitive stress events. However, isoprene-emitting plants were highly resistant to ozone-induced oxidative damage compared with their non-emitting azygous controls. In ozone-treated plants, accumulation of toxic reactive oxygen species (ROS) was inhibited, and antioxidant levels were higher. Isoprene-emitting plants showed remarkably decreased foliar damage and higher rates of photosynthesis compared to non-emitting plants immediately following oxidative stress events. An inhibition of hydrogen peroxide accumulation in isoprene-emitting plants may stall the programmed cell death response which would otherwise lead to foliar necrosis. These results demonstrate that endogenously produced isoprene provides protection from oxidative damage.