Review of the Cretaceous avian diversity of Antarctica:a changing scenario for the evolution of early Neornithine birds

The worldwide record of Cretaceous Neornithes and Neornithine-like birds is both controversial and poorly understood.However,in recent years,the Antarctic continent has yielded a substantial number of Maastrichtian avian specimens,contributing significantly to our understanding of the early evolution of this group.Simultaneously,the keen interest and collaborative efforts of various paleornithologists have resulted in a wealth of knowledge,which we have thoroughly reviewed,updated,and discussed in the context of recent discoveries.

Scale dependency of Liolaemus lizards＇ home range in response to different environmental variables

Animal habitat-use patterns cannot be isolated from scale issues. Consequently, multi-scale studies provide a complete characterization of ecological patterns that can further explain the observed variation. Liolaemus constitutes the world＇s second most speciose lizard genus. In this study, we assessed the relationships between home range size and environmental variables at 3 different spatial scales. The study at a local and regional scale was focused on the habitat specialist Liolaemus multimaculatus. The lizard＇s home range was calculated using the minimum convex polygon method in populations from grassland sites of the coastal sand dunes of the Argentinean Pampas under 2 different conditions, with or without forestations of Acacia Iongifolia. On the other hand, at a geographical scale we considered the evolutionary implications of 20 species of Liolaemus. Home range size, phylogeny, ecological, environmental, and climatic data were ob- tained from the literature and remote sensing. L. multimaculatus home range varied from 12.66 to 570.00 m. Regionally, this species had smaller home ranges in forested habitats （X： 94.02 m2） com- pared with the non-forested sites （X： 219.78m2）. Habitat structure, vegetation types, and food availability would explain the space use at finer scales. When the 20 species of Liolaernus were considered, high mean air temperature and broad thermal amplitudes showed an inverse relationship with home range size. Neither net primary productivity nor phylogeny was good predictors for home range variation at geographical scale. This study highlights the scale dependence of the explicative capability of a set of environmental and intrinsic variables on home range patterns.

Latitudinal pattern of the thermal sensitivity of running speed in the endemic lizard Liolaemus multimaculatus

Physiological performance in lizards may be affected by climate across latitudinal or altitudinal gradients.In the coastal dune barriers in central-eastern Argentina,the annual maximum environmental temperature decreases up to 2℃ from low to high latitudes,while the mean relative humidity of the air decreases from 50%to 25%.Liolaemus multimaculatus,a lizard in the family Liolaemidae,is restricted to these coastal dunes.We investigated the locomotor performance of the species at 6 different sites distributed throughout its range in these dune barriers.We inquired whether locomotor performance metrics were sensitive to the thermal regime attributable to latitude.The thermal performance breadth increased from 7%to 82%with latitude,due to a decrease in its critical thermal minimum of up to 5℃ at higher latitudes.Lizards from high latitude sites showed a thermal optimum,that is,the body temperature at which maximum speed is achieved,up to 4℃lower than that of lizards from the low latitude.At relatively low temperatures,the maximum running speed of high-latitude individuals was faster than that of low-latitude ones.Thermal parameters of locomotor performance were labile,decreasing as a function of latitude.These results show populations of L.multimaculatus adjust thermal physiology to cope with local climatic variations.This suggests that thermal sensitivity responds to the magnitude of latitudinal fluctuations in environmental temperature.

Anuran forelimb muscle tendinous structures and their relationship with locomotor modes and habitat use

The interaction between organisms and their environment is central in functional morphology.Differences in habitat usage may imply divergent morphology of locomotor systems;thus,detecting which morphological traits are conservative across lineages and which ones vary under environmental pressure is important in evolutionary studies.We studied internal and external morphology in 28 species of Neotropical anurans.Our aim was to determine if internal morphology(muscle and tendons)shows lower phylogenetic signal than external morphology.In addition,we wanted to know if morphology varies in relation to the habitat use and if there are different functional groups.We found differences in the degree of phylogenetic signal on the groups of traits.Interestingly,postaxial regions of the forelimb are evolutionarily more labile than the preaxial regions.Phylomorphospace plots show that arboreal(jumpers and graspers)and swimmer frogs cluster based on length of fingers and the lack of sesamoid,also reflected by the use of habitat.These functional clusters are also related to phylogeny.Sesamoid and flexor plate dimensions together with digit tendons showed to be important to discriminate functional groups as well as use of habitat classification.Our results allow us to identify a"grasping syndrome"in the hand of these frogs,where palmar sesamoid and flexor plate are absent and a third metacarpal with a bony knob are typical.Thus,a lighter skeleton,long fingers and a prensile hand may be key for arboreality.

Are the number and size of scales in Liolaemus lizards driven by climate?

Ectothermic vertebrates are sensitive to thermal fluctuations in the environments where they occur.To buffer these fluctuations,ectotherms use different strategies,including the integument,which is a barrier that minimizes temperature exchange between the inner body and the surrounding air.In lizards,this barrier is constituted by keratinized scales of variable size,shape and texture,and its main function is protection,water loss avoidance and thermoregulation.The size of scales in lizards has been proposed to vary in relation to climatic gradients;however,it has also been observed that in some groups of Iguanian lizards it could be related to phylogeny.Thus,here,we studied the area and number of scales(dorsal and ventral)of 60 species of Liolaemus lizards distributed in a broad latitudinal and altitudinal gradient to determine the nature of the variation of the scales with climate,and found that the number and size of scales are related to climatic variables,such as temperature and geographical variables as altitude.The evolutionary process that best explained how these morphological variables evolved was the Ornstein–Uhlenbeck model.The number of scales seemed to be related to common ancestry,whereas dorsal and ventral scale areas seemed to vary as a consequence of ecological traits.In fact,the ventral area is less exposed to climate conditions such as ultraviolet radiation or wind and is,thus,under less pressure to change in response to alterations in external conditions.It is possible that scale ornamentation,such as keels and granulosity,may bring some more information in this regard.

When a general morphology allows many habitat uses

During the last decades the study of functional morphology received more attention incorporating more detailed data corresponding to the internal anatomy that together contribute for a better understanding of the functional basis in locomotion.Here we focus on 2 lizard families,Tropiduridae and Liolaemidae,and use information re­lated to muscle-tendinous and external morphology traits of hind legs.We investigate whether the value of the traits analyzed tend to exhibit a reduced phenotypic variation produced by stabilizing selection,and whether species showing specialization in their habitat use will also exhibit special morphological features related to it.As a result,we identified that evolution of hind limb traits is mainly explained by the Ornstein-Uhlenbeck mod­el,suggesting stabilizing selection.Liolaemids and tropidurids show clear ecomorphological trends in the vari­ables considered,with sand lizards presenting the most specialized morphological traits.Some ecomorphologi­cal trends differ between the 2 lineages,and traits of internal morphology tend to be more flexible than those of external morphology,restricting the ability to identify ecomorphs shared between these 2 lineages.Conservative traits of external morphology likely explain such restriction,as ecomorphs have been historically defined in oth­er lizard clades based on variation of external morphology.

Thermal biology and locomotor performance in Phymaturus calcogaster:are Patagonian lizards vulnerable to climate change?

Behavioral and physiological traits of ectotherms are especially sensitive to fluctuations of environmental temperature.In particular,niche-specialist lizards are dependent on their physiological plasticity to adjust to changing environmental conditions.Lizards of the genus Phymaturus are viviparous,mainly herbivorous,and inhabit only rock promontories in the steppe environments of Patagonia and the Andes.Herein,we examine the vulnerability of the southernmost Phymaturus species to global warming:the endemic Phymaturus calcogaster,which lives in a mesic environment in eastern Patagonia.We studied body temperatures in the field(T_(b)),preferred body temperatures in a thermogradient(T_(pref)),the operative(T_(e))and environmental temperatures,and the dependence of running performance on body temperature.P.calcogaster had a mean T_(b)(27.04℃)and a mean Te(31.15℃)both lower than their preferred temperature(T_(pref)=36.61℃)and the optimal temperature for running performance(T_(o)=37.13℃).Lizard activity seems to be restraint during the early afternoon due high environmental temperatures.However,both,the high safety margin and warming tolerance suggest that the expected increase in environmental temperatures due to global warming(IPCC report in 2018)would not threaten,but indeed enhance locomotor performance in this population.