CMB Polarization and Theories of Gravitation with Massive Gravitons

We study in this paper three different theories of gravitation with massive gravitons - the modified Fierz-Pauli (FP) model, Massive Gravity and the bimetric theory proposed by Visser - in linear perturbation theory around a Minkowski and a flat FRW background. For the TT tensor perturbations we show that the three theories give rise to the same dynamical equations and to the same form of the Boltzmann equations for the radiative transfer in General Relativity (GR). We then analyze vector perturbations in these theories and show that they do not give the same results as in the previous case. We first show that vector perturbations in Massive Gravity present the same form as found in General Relativity, whereas in the modified FP theory the vector gravitational-wave (GW) polarization modes ($\Psi_{3}$ amplitudes in the Newman-Penrose (NP) formalism) do not decay too fast as it happens in the former case. Rather, we show that such $\Psi_{3}$ polarization modes give rise to an unusual vector Sachs-Wolfe effect, leaving a signature in the quadrupole form $Y_{2,\pm 1}(\theta,\varphi)$ on the CMB polarization. We then derive the details for the Thomson scattering of CMB photons for these $\Psi_{3}$ modes, and then construct the correspondent Boltzmann equations. Based upon these results we then qualitatively show that $\Psi_{3}$-mode vector signatures - if they do exist - could clearly be distinguished on the CMB polarization from the usual $\Psi_4$ tensor modes.Comment: To appear in Classical and Quantum Gravit

Long-term shifts in the communities of Odonata: Effect of chance or climate change?

Global climate change has been causing growing concern among conservationists for its strong implications on biodiversity alteration and loss at different levels of organization. Dragonflies and damselflies (order Odonata) occur in habitats threatened by global warming, thus they represent an ideal model organism to study the correlation patterns of climate change with taxonomic composition and the ecological functioning of communities. We carried out climate and diachronic faunistic analyses of Odonata community changes in three countries (Tunisia, Mauritania, Sweden) to test if the patterns uncovered for single assemblages as a response to local climate change may resist to the generalization across regions and latitudes. Clear climate warming occurred in the analysed regions during the last five decades. We found three main patterns of diachronic shifts in Odonata assemblage species composition based on correlative evidence: i) Generalists are likely advantaged from warming processes that cause the loss of specific habitats (i.e. temporary wetlands, cool lentic waters) and the formation of new or altered habitats suitable for pioneer species (i.e. warm and intermittent pools), whereas specialists are more likely to go toward local extinctions; ii) In Tunisia and Sweden new colonizers expanded northward from their southern distributions; iii) The Odonata communities inhabiting lentic waters are more prone to show species turnover than communities from standing waters. Our results provide new insights on the possible impact of climate change on Odonata fauna from large areas (i.e. countries) at different latitudes and represent an attempt of a generalization of the effects of climate change on Odonata range shifts and expansions. Despite that Odonata global assessment of conservation status has been completed, insufficient information is available to robustly assess all the main threats affecting their status, and extensive new field surveys are required to test if major changes in fauna composition have occurred during the last decades

Segregation structure in Odonata assemblages follows the latitudinal gradient

Latitude is known to deeply affect life with effects generalizable into ecological rules; the increasing species diversity toward tropics is the most paradigmatic. Several hypotheses tested patterns of biotic interactions’ intensity along latitude. Negative interactions (i.e. competition and predation) are expected to be among the processes that produce checkerboard distribution of species. However, no relationship between checkerboardness and latitude has been uncovered. We tested Odonata assemblages worldwide for segregation patterns using a faunistic dataset (395 species arranged in 386 natural communities) spanning a wide latitudinal range (87°). We used co-occurrence analyses (C-score index and Standardized Effect Size) as an estimate of checkerboardness then correlated the occurrence of segregation to latitude. Odonata followed the Latitudinal Diversity Gradient at the regional scale (i.e. country scale) within our analyzed assemblages spanning, whereas local richness (i.e. community scale) did not follow the same pattern. Odonata assemblages structured with segregation are more common going from high to low latitudes, and local species richness have no effect on the pattern. We summarized hypotheses on how biotic interactions or ecological and historical processes can influence the spatial patterns in the checkerboards of assemblages and presented promising ways to help to gain a better mechanistic understanding of the drivers of the Latitudinal Diversity Gradient

Can we share? Feeding strategy in three syntopic newts in artificial habitats

Natural aquatic sites are disappearing worldwide, especially in the Mediterranean region where amphibians are frequently forced to move for reproduction to artificial sites designed for irrigation and cattle watering (i.e., wells, tanks and drinking troughs). In artificial aquatic sites, where resources (space and food) are usually limited, trophic niche information can be particularly useful to infer the suitability of habitats for amphibian conservation especially when more than one species co-occurs. In this paper, we focused on three newt species: The Italian newt (Lissotriton italicus), the Italian smooth newt (Lissotriton vulgaris meridionalis) and the Italian crested newt (Triturus carnifex) inhabiting man-made wells widespread in an area in Central Italy characterized by few available natural aquatic sites. Specifically, we analyzed the trophic spectrum of the species, their interactions and overlap, and discussed the potential role of wells in amphibian conservation. Overall, 550 newt individuals occurring in 16 distinct wells were sampled. The study species consumed similar resources, mainly of aquatic origin, with Diptera larvae and Cladocera representing the most important preys. The high degree of diet overlap observed may be due to site oligotrophy and high availability of small-sized prey, and it does not necessarily lead to competition. Newts had similar narrow niche width values and a generalist feeding pattern with high diversity among individuals. Lissotriton italicus and T. carnifex showed wider niche width in isolation than in syntopy condition, probably as a result of interspecific competition and/or intraguild predation. We showed that artificial aquatic sites are important for newt ecology and conservation since they allow up to three species to cohabit, thus representing a good surrogate of natural habitats. The study wells apparently provided suitable trophic conditions for newts in terms of prey availability and catchability. To date, just a few studies have contributed to a greater understanding of newts’ diet in artificial aquatic sites and this gap of knowledge has to be filled to clarify their role in amphibian ecology and conservation

Biological responses in pesticide exposed lizards (Podarcis siculus)

The release of contaminants as herbicides, fungicides and insecticides into the environment has been listed as one of the six major contributors to the global decline of reptiles. Although reptiles may face severe risk from contaminants due to their ecology and physiology, they are currently less studied than other vertebrate groups. In the present work, we investigated if and how different types of field treatment (conventional and organic) affected the health status of Italian wall lizard (Podarcis siculus) individuals in central Italy. We chose a multi-biomarker approach that evaluated the biological responses of lizards to the treatment by means of AChE activity in the nervous system, biotransformation enzymes activities and oxidative stress in the liver, micronuclei frequency measured in the erythrocytes, and rate of intestinal parasitic infection. Our findings showed evidence of effects of treatment in conventional areas and between sexes with significant oxidative stress due to hydroxyl radicals, that caused DNA damage. No difference of intestinal parasite infections was found among treatments. Podarcis siculus seems to be a good bioindicator in ecotoxicological studies and potentially in risk assessment of pesticides, although further analyses in laboratory and in the field are needed to achieve more accurate quantification of specific pesticide effects in relation to known exposure history and to understand if other mechanisms were involved in the toxicity and detoxification process of pesticides for this species

Living with aliens: Suboptimal ecological condition in semiaquatic snakes inhabiting a hot spot of allodiversity

The presence of alien species can embody a form of disturbance for natural communities and the concomitant presence of alien species at different levels within the trophic chain may compromise ecosystem functionality. We studied the ecology of two species of snake (Natrix tessellata and N. natrix) in a system of five ponds with a high number of alien species at a Mediterranean area in central Italy. We evaluated the potential perturbations to ecological traits of snakes due to the presence of alien species, including their body size, population density, and food habits. We compared the studied populations' body size to that estimated in conspecific populations studied elsewhere, including populations at close distance from the study site. Distance sampling and Capture-Mark-Recapture techniques were used to calculate the population density. Diet was estimated using stomach contents and stable isotope ratios (δ 15 N and δ 13 C), using Bayesian stable isotope mixing models to estimate the contribution of food sources and species' isotopic niche spaces. Few prey items were found in the stomach contents of either species, with Ameiurus melas as the main prey. Based on isotope niche analyses, N. tessellata diet consisted of only alien species, and N. natrix diet mostly relied on alien species (> 80%). Stomach contents revealed high overlap between the two species, although isotopes showed a random resource use (i.e. low isotopic niche space overlap). Overall, we caught a low number of individuals, indicating small population sizes. Moreover, snakes at the study site were comparatively smaller in size than most other populations found in the literature and almost all the recorded individuals were in very poor condition or injured by ingested alien prey. We suggest that the presence of rich allodiversity has negatively affected the snakes' fitness by decreasing their foraging performance, increasing their risk of being preyed upon, or through other mechanisms

Trophic structure of a pond community dominated by an invasive alien species: Insights from stomach content and stable isotope analyses

Invaders affect native species across multiple trophic levels, influencing the structure and stability of freshwater communities. Based on the 'trophic position hypothesis', invaders at the top of the food web are more harmful to native species via direct and indirect effects than trophically analogous native predators are.However, introduced and native predators can coexist, especially when non-native species have no ecological and behavioural similarities with natives, occupy an empty niche, or natives show generalist anti-predator strategies that are effective at the community level.At present, conservation efforts are focused on eradicating invaders; however, their removal may lead to unwanted and unexpected outcomes, especially when invaders are well established and strongly interspersed with natives. This highlights the need to consider invaders in a whole-ecosystem context and to consider the evolutionary history and behavioural ecology of natives and invaders before active management is applied.Here, stomach content and stable isotope analyses were combined to investigate a pond system dominated by invaders in order to understand the effects of the interactions among upper level predators and lower level members of the food web on the whole community structure.Both diet and isotope analyses showed that several invaders contributed to the diet of natives and invaders. A significant isotope overlap was found among upper level predators. However, stomach content analysis suggested that predators reduced the potential competition differentiating the food spectrum by including additional prey in their diet. Both native and non-native upper level predators, by preying on invaders, seem not to exert a strong suppressive effect through predation and competition on native species.This research confirms the importance of studying food webs to identify ecological conditions that forecast the potential for deleterious impacts before management is applied. In cases where invaders cannot be eradicated, management efforts should follow a conciliatory approach promoting the coexistence of native species with invaders

Living with aliens: Suboptimal ecological condition in semiaquatic snakes inhabiting a hot spot of allodiversity

The presence of alien species can embody a form of disturbance for natural communities and the concomitant presence of alien species at different levels within the trophic chain may compromise ecosystem functionality. We studied the ecology of two species of snake (Natrix tessellata and N. natrix) in a system of five ponds with a high number of alien species at a Mediterranean area in central Italy. We evaluated the potential perturbations to ecological traits of snakes due to the presence of alien species, including their body size, population density, and food habits. We compared the studied populations' body size to that estimated in conspecific populations studied elsewhere, including populations at close distance from the study site. Distance sampling and Capture-Mark-Recapture techniques were used to calculate the population density. Diet was estimated using stomach contents and stable isotope ratios (δ15N and δ13C), using Bayesian stable isotope mixing models to estimate the contribution of food sources and species' isotopic niche spaces. Few prey items were found in the stomach contents of either species, with Ameiurus melas as the main prey. Based on isotope niche analyses, N. tessellata diet consisted of only alien species, and N. natrix diet mostly relied on alien species (>80%). Stomach contents revealed high overlap between the two species, although isotopes showed a random resource use (i.e. low isotopic niche space overlap). Overall, we caught a low number of individuals, indicating small population sizes. Moreover, snakes at the study site were comparatively smaller in size than most other populations found in the literature and almost all the recorded individuals were in very poor condition or injured by ingested alien prey. We suggest that the presence of rich allodiversity has negatively affected the snakes’ fitness by decreasing their foraging performance, increasing their risk of being preyed upon, or through other mechanisms

Mitochondrial ghost lineages blur phylogeography and taxonomy of Natrix helvetica and N. natrix in Italy and Corsica

Grass snakes are widely distributed across the Western Palearctic. Recent phylogeographic studies provided evidence that three distinct parapatric species exist. Two of these occur in Italy, Natrix helvetica and N. natrix, and a contact zone between both taxa has been suggested for north-eastern Italy. Moreover, previous investigations revealed for the Italian Peninsula a complex phylogeographic structure. Using mtDNA sequences and microsatellite loci, we examined the situation for mainland Italy, Sicily, Sardinia, and Corsica. Our study confirmed the occurrence of N. natrix in north-eastern Italy. Cline analyses revealed limited gene flow between N. helvetica and N. natrix across a narrow hybrid zone. Within N. helvetica, conflicting patterns of mitochondrial and nuclear genomic differentiation were revealed. Three nuclear genomic clusters were found; one of them corresponded to no fewer than five distinct and, in part, deeply divergent and ancient mitochondrial lineages from mainland Italy and Sicily. This cluster was paraphyletic with respect to the two remaining mitochondrial lineages, each of which matched with another nuclear genomic cluster (one from Corsica plus Sardinia and another one from western Europe north of the Alps). This unexpected pattern most likely results from mainly male-mediated gene flow and female philopatry combined with population-density-dependent processes such as ‘high-density blocking’. With respect to taxonomy, we propose to synonymize N. h. lanzai Kramer, 1970 with N. h. sicula (Cuvier, 1829), acknowledging their lacking nuclear genomic differentiation. The studied hybrid zone of N. h. helvetica and N. h. sicula in Italy is wide, with a smooth cline for nuclear markers, supporting their subspecies status. We found no evidence for the distinctiveness of the two subspecies from Corsica (N. h. corsa) and Sardinia (N. h. cetti), suggesting their synonymy, but refrain from taxonomic conclusions because of small sample sizes and the endangered status of the Sardinian taxon