Effects of landscape features and demographic history on the genetic structure of Testudo marginata populations in the southern Peloponnese and Sardinia

Testudo marginata, the largest European land tortoise, is suffering habitat degradation and destruction. Some populations, in markedly degraded habitats, are characterized by divergent morphotypes. However, the evolutionary significance of these morphotypes is of debate. Using 11 polymorphic microsatellites, we studied: (1) marginated tortoises from Sardinia that display a divergent morphotype – this population was potentially introduced from Greece; and (2) an area in the southern Peloponnese that includes a small and degraded zone in which marginated tortoises are dwarf. Genetic analyses run without any a priori assignment clearly acknowledge the specimens sampled in the territory of the dwarf form as a single group whilst Sardinian specimens are clustered with other specimens from the northern part of the area sampled in Greece. Demographic analyses suggest that Sardinian tortoises originated recently from some of the populations sampled in the northern part of the area sampled in Greece. Over locations sampled in Greece, a landscape‐genetic analysis allowed us to detect potential landscape features that may reduce gene flow between the dwarf form territory and surrounding areas. Our results suggest that the territory of the dwarf form is particularly propitious for marginated tortoises and that conservation regulations in Greece should be reinforced to protect this area from increasing impact of human activities changing from traditional agriculture to mechanization and extensive use of chemicals. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 591–606.     

WATER EXCHANGE, TEMPERATURE TOLERANCE, OXYGEN CONSUMPTION AND ACTIVITY OF THE NAMIB DESERT SNAIL, TRIGONEPHRUS SP.

Water exchange, temperature tolerance and oxygen consumptionof the snail, Trigonephrus sp., from the southern Namib desertof Namibia were examined and related to activity. At 25°Cand 15% R.H. mean water loss and food and water uptake were5.95 mg. day^–1 and 630 mg.day^–1, respectively. Bodytemperature tracked sand temperature. Snails tolerated sandtemperatures as high as 45°C. Mean ± S.D. oxygenconsumption rates were 32.0 ± 2.94 µlO₂.g totalbody mass^–1.h^–1 at 15°C, when the snails wereactive, and 11.27 µlO₂.g total body mass^–1.h^–1at 25°C, when the snails were inactive. These values are2-6 times lower than those recorded for the similarly sizedmesic snail, Helix aspersa. Activity experiments indicated thatlow ambient temperatures and high humidities were favoured bythe snails. This, together with the burying behaviour of thesesnails during high temperatures, suggests that they limit stressby restricting activity to physiologically-favourable periods,even though more-extreme conditions may be tolerated. (Received 7 June 1990; accepted 20 November 1990)     

Tapetal Organization During Sporogenesis in Psilotum nudum

Stages in the differentiation of the tapetum of Psilotum nudumare described. Two concurrently occurring components of thetapetum can be recognized. A plasmodial tapetum with associatedfunctional nuclei develops within the sporangial loculus duringthe early stages of differentiation, appears to remain viablefor several months, that is during the entire period of sporogenesis,and undergoes reorganization on three occasions. During MeiosisI groups of spore mother cells are enclosed in clear areas withinthe plasmodium: by the end of Meiosis II each tetrad is isolatedin a plasmodial chamber; and, finally, mature spores are enclosedwithin individual tapetal chambers. Typically enlarged cellsare present during the development of a cellular, parietal tapetum.A sporopollenin-containing layer or tapetal membrane characteristicof a secretory tapetum develops on the inner tangential walland lines the surface of the loculus. This tapetal membranepersists even after dehiscence of the sporangium. These observationsare discussed in relation to previously published conflictingdata and may be relevant to the arguments concerning the relationshipof the Psilotaceae to the Filicales. Psilotum nudum, light microscopy, parietal tapetum, plasmodial tapetum, tapetal membrane, tapetal reorganization, sporogenesis, sporopollenin     

Inhibition of Leishmania Donovani Amastigote-To-Promastigote Transformation By Infected Hamster Spleen Lymphocyte Lysates*

SYNOPSIS Leishmania donovani amastigote-to-promastigote transformation is inhibited by homogenates of infected hamster liver and spleen. This inhibitory activity is localized in the 100,000 g pellet fraction. Tests with lysates of adherent (macrophyages) and nonadherent (lymphocytes) spleen cells indicated that the inhibitory activity resided in the lymphocytes, specifically in the 100,000 g pellet fraction.     

Ecosystem engineering by beavers affects mayfly life histories

1. The North American beaver has been studied as a model ecosystem engineer for many decades. Previous studies have documented physical, chemical and biological impacts attributed to beaver engineering in both aquatic and terrestrial environments. This study focused on the effects of ecosystem engineering by beavers on life histories of a common mayfly and on the potential consequences for mayfly populations. 2. We studied 18 montane beaver ponds of varying size and shape in western Colorado near the Rocky Mountain Biological Laboratory. Our goal was to test whether variation in beaver pond morphology (pond size and shape) explains downstream changes in stream temperature, mayfly size and timing of emergence. 3. Downstream water temperatures varied predictably with pond morphology, being colder downstream of high‐head dams and warmer downstream of low‐head dams. Pond morphology was also a significant predictor of variation in the size of mature female Baetis bicaudatus (the most abundant mayfly), with larger females emerging downstream of high‐head dams and smaller females downstream of low‐head dams. The size of male B. bicaudatus was not significantly related to pond morphology or stream temperature. There was no relationship between pond morphology and variation in the timing of emergence of Baetis (males or females) between upstream and downstream reaches. 4. Our results have implications for the effects of beaver ponds on Baetis individual fitness because large Baetis females are more fecund. Therefore, predictable female size variation associated with beaver pond morphology makes it possible to model the effects of beaver activity on local contributions of Baetis to the regional pool of reproductive adults at the catchment scale. Additionally, predictable changes in the size of emerging mayflies may have important consequences for the magnitude of aquatic to terrestrial resource subsidies in beaver‐modified systems.     

Flow variability maintains the structure and composition of in‐channel riparian vegetation

1. Naturally variable river flows are considered to be important for structuring riparian vegetation. However, while the importance of floods for the ecology of riparian vegetation is well recognised, much less is known about the importance of small fluctuations in river flows. 2. We investigated the effect of water supply diversion weirs on the riparian vegetation of upland streams. These weirs remove within‐channel fluctuations in flow but do not prevent large floods downstream. We surveyed the in‐channel and banktop vegetation of five streams, three of which were regulated by weirs and two of which acted as controls. 3. Unexpectedly, we observed greater species richness within the channel downstream of the weirs. This was because of increased numbers of exotic and terrestrial (‘dry’) plant species. Grass cover was also greater downstream of the weirs. There were no significant differences in the banktop vegetation between the upstream and downstream sites of the regulated streams. 4. Our results highlight the role of within‐channel flow variability in maintaining the composition of vegetation within the stream channel. We suggest that greater species richness does not necessarily indicate a less‐disturbed environment. Rather, a greater number of ‘dry’ species is indicative of the impacts of flow regulation. 5. Small fluctuations in river flows are probably necessary to protect the ecosystem structure and function of regulated streams. It is recommended that variable within‐channel flows be provided in regulated streams.     

Chromosomal evolution of South American frugivorous butterflies in the Satyroid clade (Nymphalidae: Charaxinae, Morphinae and Satyrinae)

We describe the chromosome numbers of a monophyletic group of Satyroid subfamilies of primary fruit-attracted butterflies from South America: Charaxinae, Morphinae (including Brassolini) and Satyrinae. The charaxines do not have a distinct modal number. Their chromosome numbers are in the range n  = 6–50, with n  = 7–9, n  = 12, n  = 16, n  = 19–21, n  = 26, and n  = 28–31 being the most common numbers. Within the Morphinae, the Morphini have a modal n  = 28 and the Brassolini a modal n  = 29, with few exceptions. The Neotropical satyrines, in particular the basal species, have a weak modal n  = 29, which is a strong modal number in Palearctic satyrines. The African satyrines have an equally strong modal n  = 28. Most Neotropical satyrines have, like charaxines, chromosome numbers lower than the weak modal n  = 29, and often half this modal, but there are genera with stable numbers among the satyrines and charaxines. Evidently, the Neotropical satyroids descend from basal Nymphalidae with the typical lepidopteran modal number of n  = 31, which have also given rise to the Heliconiini with modal n  = 31 and 21 and Ithomiinae with modal numbers of n  = 14–15.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 92 , 467–481.     

First pairing in Snow Geese Anser caerulescens: at what age and at what time of year does it occur?

In migratory birds, the place and time of pair formation are important parameters for population structure and dynamics. Geese are not only migratory but also exhibit long-term monogamy, and therefore the first pairing event in a bird's lifetime is of particular importance. Through behavioural observations of young, known-age, marked birds conducted on the wintering grounds during three winter seasons we investigated two aspects of the timing of first pair formation in the Wrangel Island population of Snow Geese Anser caerulescens : (1) the age at which birds first form pair bonds, and (2) the seasonal pattern of first pair formation. Wrangel Island Snow Geese paired considerably later in life than Snow Geese from a low-Arctic population: almost none of the birds formed pairs in their second winter, and many were still in sibling groups for at least part of that season. The proportion of birds in pairs continued to increase until at least 5 years of age. Most pairing took place during the observation periods, and in general the proportion of birds in pair bonds increased gradually throughout the winter season. The amount of pairing during spring migration or summer varied annually and among cohorts, indicating that even very young birds may be able to form pair bonds quickly if conditions on the breeding grounds are unusually favourable. Pairing later and remaining in family groups longer may be a response to breeding conditions in this high-Arctic colony. Here, productivity is typically low due to harsh weather and predation, whereas Snow Geese breeding in the low Arctic are less restricted and form pairs and start to breed when younger. The fact that most, but not all, pairing takes place on the wintering grounds helps explain why a previous study found a certain amount of gene flow between the two Wrangel Island subpopulations with separate wintering grounds.