Shared geographic histories and dispersal contribute to congruent phylogenies between amphipods and their microsporidian parasites at regional and global scales

In parasites that strongly rely on a host for dispersal, geographic barriers that act on the host will simultaneously influence parasite distribution as well. If their association persists over macroevolutionary time it may result in congruent phylogenetic and phylogeographic patterns due to shared geographic histories. Here, we investigated the level of congruent evolutionary history at a regional and global scale in a highly specialised parasite taxon infecting hosts with limited dispersal abilities: the microsporidians Dictyocoela spp. and their amphipod hosts. Dictyocoela can be transmitted both vertically and horizontally and is the most common microsporidian genus occurring in amphipods in Eurasia. However, little is known about its distribution elsewhere. We started by conducting molecular screening to detect microsporidian parasites in endemic amphipod species in New Zealand; based on phylogenetic analyses, we identified nine species‐level microsporidian taxa including six belonging to Dictyocoela. With a distance‐based cophylogenetic analysis at the regional scale, we identified overall congruent phylogenies between Paracalliope, the most common New Zealand freshwater amphipod taxon, and their Dictyocoela parasites. Also, hosts and parasites showed similar phylogeographic patterns suggesting shared biogeographic histories. Similarly, at a global scale, phylogenies of amphipod hosts and their Dictyocoela parasites showed broadly congruent phylogenies. The observed patterns may have resulted from covicariance and/or codispersal, suggesting that the intimate association between amphipods and Dictyocoela may have persisted over macroevolutionary time. We highlight that shared biogeographic histories could play a role in the codiversification of hosts and parasites at a macroevolutionary scale.     

Testing the Performance of Fourteen Native Tropical Tree Species in Two Abandoned Pastures of the Lacandon Rainforest Region of Chiapas,Mexico

The rainforest of Mexico has been degraded and severely fragmented, and urgently require restoration. However, the practice of restoration has been limited by the lack of species‐specific data on survival and growth responses to local environmental variation. This study explores the differential performance of 14 wet tropical early‐, mid‐ or late‐successional tree species that were grown in two abandoned pastures with contrasting land‐use histories. After 18 months, seedling survival and growth of at least 7 of the 14 tree species studied were significantly higher in the site with a much longer history of land use (site 2). Saplings of the three early‐successional species showed exceptional growth rates. However, differences in performance were noted in relation to the differential soil properties between the experimental sites. Mid‐successional species generally showed slow growth rates but high seedling survival, whereas late‐successional species exhibited poor seedling survival at both the study sites. Stepwise linear regressions revealed that the species integrated response index combining survivorship and growth measurements, was influenced mostly by differences in soil pH between the two abandoned pastures. Our results suggest that local environmental variation among abandoned pastures of contrasting land‐use histories influences sapling survival and growth. Furthermore, the similarity of responses among species with the same successional status allowed us to make some preliminary site and species‐specific silvicultural recommendations. Future field experiments should extend the number of species and the range of environmental conditions to identify site “generalists” or more narrowly adapted species, that we would call “sensitive.”     

Update on the challenging role of biofilms in peritoneal dialysis

Biofilms are commonly associated with an increased risk of patient infection. In peritoneal dialysis (PD), catheter associated infection, especially peritonitis, remains a clinically relevant problem. Although the presence of a biofilm is recognized in relapsing, repeat, and catheter-related peritonitis, it remains poorly characterized. In this review, an update on the role of biofilms in PD infections is presented. The emerging concept that host cells and tissue associated biofilms, in addition to the biofilms on the catheters themselves, contribute to the recalcitrance of infections is discussed. Furthermore, the evidence of biofilms on PD catheters, their developmental stages, and the possible influence of the PD environment are reviewed. The focus is given to ex vivo and in vitro studies that contribute to the elucidation of the interplay between host, microbial, and dialysis factors. The key issues that are still to be answered and the challenges to clinical practice are discussed.     

Does Nocturnality Drive Binocular Vision? Octodontine Rodents as a Case Study

Binocular vision is a visual property that allows fine discrimination of in-depth distance (stereopsis), as well as enhanced light and contrast sensitivity. In mammals enhanced binocular vision is structurally associated with a large degree of frontal binocular overlap, the presence of a corresponding retinal specialization containing a fovea or an area centralis, and well-developed ipsilateral retinal projections to the lateral thalamus (GLd). We compared these visual traits in two visually active species of the genus Octodon that exhibit contrasting visual habits: the diurnal Octodon degus, and the nocturnal Octodon lunatus. The O. lunatus visual field has a prominent 100° frontal binocular overlap, much larger than the 50° of overlap found in O. degus. Cells in the retinal ganglion cell layer were 40% fewer in O. lunatus (180,000) than in O. degus (300,000). O. lunatus has a poorly developed visual streak, but a well developed area centralis, located centrally near the optic disk (peak density of 4,352 cells/mm²). O. degus has a highly developed visual streak, and an area centralis located more temporally (peak density of 6,384 cells/mm²). The volumes of the contralateral GLd and superior colliculus (SC) are 15% larger in O. degus compared to O. lunatus. However, the ipsilateral projections to GLd and SC are 500% larger in O. lunatus than in O. degus. Other retinorecipient structures related to ocular movements and circadian activity showed no statistical differences between species. Our findings strongly suggest that nocturnal visual behavior leads to an enhancement of the structures associated with binocular vision, at least in the case of these rodents. Expansion of the binocular visual field in nocturnal species may have a beneficial effect in light and contrast sensitivity, but not necessarily in stereopsis. We discuss whether these conclusions can be extended to other mammalian and non-mammalian amniotes.     

Microstructural morphology in early dermal denticles of hammerhead sharks (Elasmobranchii: Sphyrnidae) and related taxa

Mello, W.C., de Carvalho, J.J., Brito, P.M.M. 2011. Microstructural morphology in early dermal denticles of hammerhead sharks (Elasmobranchii: Sphyrnidae) and related taxa. —Acta Zoologica (Stockholm) 00 : 1–7. This study uses scanning electron microscopies to investigate and describe the microstructural diversity of dermal denticles in the family Sphyrnidae, which comprises all living hammerhead shark species, comparing them to other related taxa (i.e. Carcharhinus dussumieri, Carcharhinus plumbeus, Carcharhinus acronotus, Rhizoprionodon acutus, Negaprion brevirostris and Hemigaleus microstoma). The results reveal that sphyrnids present noticeable microstructures in the dermal denticles, distinguishing them from the other related species investigated. Additionally, scale patterns are the same in three distinct body regions (i.e. cephalic, branchial and dorsal fin). Species of Sphyrnidae that reach bigger total lengths and that are widely distributed (i.e. Sphyrna lewini and Sphyrna mokarran) presented more, smaller and nearly hexagonal microstructures that do not cover the entire scale surface, unlike species reaching smaller sizes and restricted to coastal habits (i.e. Sphyrna tiburo, Sphyrna tudes, Sphyrna media and Eusphyra blochii). The sphyrnid scales are similar to R. acutus and C. dussumieri rather than to the other species, but it is not possible to identify the sphyrnid species only by scale features. It is clear that a similar morphology of scales is not necessarily related to similar life habits, and that they are candidates to provide new characters in phylogenetical studies among sphyrnids.     

Parasitism Behavior of Tetrastichus howardi (Hymenoptera: Eulophidae) on Larvae and Pupae of Sugarcane Borers

Journal of Insect Behavior - Control of the sugarcane borers, Diatraea saccharalis and Diatraea impersonatella (= D. flavipennella) (Lepidoptera: Crambidae), in Brazil, is based on mass release of...     

The Role of Historical Barriers in the Diversification Processes in Open Vegetation Formations during the Miocene/Pliocene Using an Ancient Rodent Lineage as a Model

The Neotropics harbors a high diversity of species and several hypotheses have been proposed to account for this pattern. However, while species of forested domains are frequently studied, less is known of species from open vegetation formations occupying, altogether, a larger area than the Amazon Forest. Here we evaluate the role of historical barriers and the riverine hypothesis in the speciation patterns of small mammals by analyzing an ancient rodent lineage (Thrichomys, Hystricomorpha). Phylogenetic and biogeographic analyses were carried out with mitochondrial and nuclear DNA markers to analyze the evolutionary relationships between Thrichomys lineages occurring in dry domains along both banks of the Rio São Francisco. This river is one of the longest of South America whose course and water flow have been modified by inland tectonic activities and climate changes. Molecular data showed a higher number of lineages than previously described. The T. inermis species complex with 2n = 26, FN = 48 was observed in both banks of the river showing a paraphyletic arrangement, suggesting that river crossing had occurred, from east to west. A similar pattern was also observed for the T. apereoides complex. Thrichomys speciation occurred in Late Miocene when the river followed a different course. The current geographic distribution of Thrichomys species and their phylogenetic relationships suggested the existence of frequent past connections between both banks in the middle section of the Rio São Francisco. The extensive palaeodune region found in this area has been identified as a centre of endemism of several vertebrate species and is likely to be a center of Thrichomys diversification.