Global Protected Areas as refuges for amphibians and reptiles under climate change

Protected Areas (PAs) are the cornerstone of biodiversity conservation. Here, we collated distributional data for >14,000 (~70% of) species of amphibians and reptiles (herpetofauna) to perform a global assessment of the conservation effectiveness of PAs using species distribution models. Our analyses reveal that >91% of herpetofauna species are currently distributed in PAs, and that this proportion will remain unaltered under future climate change. Indeed, loss of species' distributional ranges will be lower inside PAs than outside them. Therefore, the proportion of effectively protected species is predicted to increase. However, over 7.8% of species currently occur outside PAs, and large spatial conservation gaps remain, mainly across tropical and subtropical moist broadleaf forests, and across non-high-income countries. We also predict that more than 300 amphibian and 500 reptile species may go extinct under climate change over the course of the ongoing century. Our study highlights the importance of PAs in providing herpetofauna with refuge from climate change, and suggests ways to optimize PAs to better conserve biodiversity worldwide.

The Macroecology of Chemical Communication in Lizards: Do Climatic Factors Drive the Evolution of Signalling Glands?

Chemical communication plays a pivotal role in shaping sexual and ecological interactions among animals. In lizards, fundamental mechanisms of sexual selection such as female mate choice have rarely been shown to be influenced by quantitative phenotypic traits (e.g., ornaments), while chemical signals have been found to potentially influence multiple forms of sexual and social interactions, including mate choice and territoriality. Chemical signals in lizards are secreted by glands primarily located on the edge of the cloacae (precloacal glands, PG) and thighs (femoral glands), and whose interspecific and interclade number ranges from 0 to > 100. However, elucidating the factors underlying the evolution of such remarkable variation remains an elusive endeavour. Competing hypotheses suggest a dominant role for phylogenetic conservatism (i.e., species within clades share similar numbers of glands) or for natural selection (i.e., their adaptive diversification results in deviating numbers of glands from ancestors). Using the prolific Liolaemus lizard radiation from South America (where PG vary from 0 to 14), we present one of the largest-scale tests of both hypotheses to date. Based on climatic and phylogenetic modelling, we show a clear role for both phylogenetic inertia and adaptation underlying gland variation: (i) solar radiation, net primary productivity, topographic heterogeneity and precipitation range have a significant effect on PG variation, (ii) humid and cold environments tend to concentrate species with a higher number of glands, (iii) there is a strong phylogenetic signal that tends to conserve the number of PG within clades. Collectively, our study confirms that the inertia of niche conservatism can be broken down by the need of species facing different selection regimes to adjust their glands to suit the demands of their specific environments.

What defines an adaptive radiation? Macroevolutionary diversification dynamics of an exceptionally species-rich continental lizard radiation

BACKGROUND

Adaptive radiation theory posits that ecological opportunity promotes rapid proliferation of phylogenetic and ecological diversity. Given that adaptive radiation proceeds via occupation of available niche space in newly accessed ecological zones, theory predicts that: (i) evolutionary diversification follows an 'early-burst' process, i.e., it accelerates early in the history of a clade (when available niche space facilitates speciation), and subsequently slows down as niche space becomes saturated by new species; and (ii) phylogenetic branching is accompanied by diversification of ecologically relevant phenotypic traits among newly evolving species. Here, we employ macroevolutionary phylogenetic model-selection analyses to address these two predictions about evolutionary diversification using one of the most exceptionally species-rich and ecologically diverse lineages of living vertebrates, the South American lizard genus Liolaemus.

RESULTS

Our phylogenetic analyses lend support to a density-dependent lineage diversification model. However, the lineage through-time diversification curve does not provide strong support for an early burst. In contrast, the evolution of phenotypic (body size) relative disparity is high, significantly different from a Brownian model during approximately the last 5 million years of Liolaemus evolution. Model-fitting analyses also reject the 'early-burst' model of phenotypic evolution, and instead favour stabilizing selection (Ornstein-Uhlenbeck, with three peaks identified) as the best model for body size diversification. Finally, diversification rates tend to increase with smaller body size.

CONCLUSIONS

Liolaemus have diversified under a density-dependent process with slightly pronounced apparent episodic pulses of lineage accumulation, which are compatible with the expected episodic ecological opportunity created by gradual uplifts of the Andes over the last ~25My. We argue that ecological opportunity can be strong and a crucial driver of adaptive radiations in continents, but may emerge less frequently (compared to islands) when major events (e.g., climatic, geographic) significantly modify environments. In contrast, body size diversification conforms to an Ornstein-Uhlenbeck model with multiple trait optima. Despite this asymmetric diversification between both lineages and phenotype, links are expected to exist between the two processes, as shown by our trait-dependent analyses of diversification. We finally suggest that the definition of adaptive radiation should not be conditioned by the existence of early-bursts of diversification, and should instead be generalized to lineages in which species and ecological diversity have evolved from a single ancestor.

Reversibility of elemental liquid diet-enhanced methotrexate toxicity by refeeding with chow

The toxic effects of methotrexate administration [20 mg/kg, bolus intraperitoneally (ip)] to rats fed a regular chow diet (n = 10) was compared with results in animals fed an elemental, chemically defined, liquid diet (n = 10) for 7 days. All animals receiving an elemental diet became anorectic and lethargic within 60 hr of methotrexate injection. All animals in this group subsequently developed enteritis and died within 150 hr. There was no clinical evidence of enteritis in rats fed a regular chow diet and mortality as zero in this group (p less than 0.001). In a second study one group of rats (n = 9) was fed a regular chow diet for 7 days; four groups were fed an elemental, chemically defined, liquid diet (n = 9 per group) for 7 days. At 24 hr and 8 hr prior to, or 24 hr after methotrexate administration, one group was refed a regular chow diet; the fourth group was maintained on an elemental liquid diet throughout the study period. All rats fed a regular chow diet survived following methotrexate injection (20 mg/kg, ip). All rats fed an elemental diet throughout the study period died. Those rats refed a regular diet 24 or 8 hr prior to methotrexate injection demonstrated a significant improvement in survival (100% in the 24-hr group, 55% in the 8-hr group). However, those animals refed a regular diet 24 hr after methotrexate injection demonstrated a 100% mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Alteration of methotrexate toxicity in rats by manipulation of dietary components

Administration of a chemically defined, elemental diet to rats given 20 mg/kg of methotrexate intraperitoneally has consistently resulted in a 100% mortality from severe enteritis within 156 h. This study examined the importance of specific dietary components in the etiology of this enhanced toxicity. Rats were given their respective diets for 7 days, whereupon methotrexate (20 mg/kg) was given intraperitoneally, and percent of survivors was recorded. Varying the concentration of carbohydrate as polysaccharide (0%, 50%, 100%) (n = 30) had no effect on survival. An increase in the percent of protein as polypeptide (0%, 25%, 50%, 75%, 100%) (n = 50) in the elemental diet resulted in a progressively significant increase in percent survival. Addition of either fat or bulk to this elemental diet had no effect on survivorship. Serum and bile methotrexate levels of rats fed an elemental liquid diet (whether or not all of the protein was provided as polypeptide) were significantly increased from 12 to 72 h (p less than 0.03) compared with rats fed a regular Chow diet. When the protein content of the elemental liquid diet was provided as 100% polypeptide, serum and bile methotrexate levels were significantly lower at 48 h compared with the elemental diet group given 100% of protein as amino acid. Administration of methotrexate to rats fed an elemental liquid diet in which all of the protein is provided as amino acids is extremely toxic to the gastrointestinal tract, probably as a result of delayed clearance of the drug from the systemic circulation and from bile. This toxicity is alleviated by the provision of protein as polypeptide in the elemental diet. No toxicity to the drug is seen at this dose in rats fed a regular Chow diet. If these results are applicable to humans, the use of elemental liquid diets as the only source of enteral nutrition would appear contraindicated in patients receiving methotrexate.

Indirect calorimetry: comparison of hood and mask systems for measuring resting energy expenditure in healthy volunteers

Controversy exists as to the validity and reliability of hood and mask systems in measuring indirect calorimetry. The purpose of this study was to evaluate the accuracy and reproducibility of repeat measurements of resting energy expenditure (REE) in volunteers. Paired REE measurements were performed in 23 subjects after an overnight fast using hood and mask systems. Lean body mass was calculated from four skinfold measurements and body weight determinations. Data were normalized to body weight and lean body mass and were calculated as percent predicted REE in paired tests taken within 5 minutes on the same subject. No significant difference in mean REE was noted between hood and mask systems. Linear regression analysis showed a strong positive correlation (r = 0.91, p less than 0.001) between hood and mask measurements of REE.

Alteration of chemotherapy toxicity using a chemically defined liquid diet in rats

Controversy exists as to whether administration of a chemically defined diet alters toxicity to chemotherapy. The purpose of this study was to evaluate toxicity to methotrexate in rats fed a chemically defined liquid diet or a regular chow diet. In the first study, 48 adult rats were randomized to be fed a chemically defined liquid diet or a regular diet for 14 days when methotrexate (25 or 50 mg/kg) was given. All liquid diet rats became anorexic and died within 96 h, while no deaths were observed in rats fed regular diet. When 20 liquid diet and regular diet rats were pair-fed to equalize caloric intake before and after methotrexate administration, similar mortality results occurred. In a second study, methotrexate (50 mg/kg) or saline was given and 60 h later all animals were sacrificed to obtain small bowel luminal cultures and tissue sections for histological evaluation. Administration of the liquid diet altered small bowel flora to predominantly Escherichia coli and Pseudomonas sp. and histology showed severe small bowel mucosal enteritis in comparison with regular diet rats. To evaluate whether the changes in intestinal flora or alterations in drug pharmacokinetics were responsible for the increased mortality, two additional studies were done. Gentamicin (4.8 mg/kg/day) was given p.o. or i.m. to the rats on the chemically defined liquid diet. A significant reduction of intraluminal bacteria occurred, but survival time was not improved in animals receiving antibiotics. When mean serum methotrexate levels were analyzed in non-antibiotic-treated rats, drug concentrations were significantly increased at 24, 36, and 48 h after methotrexate injection in the elemental liquid diet rats compared with chow diet rats. Administration of a chemically defined liquid diet to rats receiving methotrexate increased the occurrence and severity of intestinal enteritis, altered intraluminal bowel flora, and decreased clearance of methotrexate from the serum.

Human energy requirements: overestimation by widely used prediction equation

Basal energy expenditure accounts for a large component of energy losses, and a clinical estimate of this form of thermogenesis is usually derived from a prediction equation. The most widely used prediction equation was developed in 1919 by Harris and Benedict. The energy requirements of healthy and diseased individuals are often estimated from application of this formula. Using a direct gradient-layer calorimeter and two different indirect calorimeters, our two centers found that the Harris-Benedict equation overestimated basal energy requirements by 10 to 15% (X +/- SD, 12.3 +/- 11%) in 201 studies of healthy men and women. These results raise questions regarding the accuracy of predicting an individual's energy requirements.