During several surveys made in the region of the lower Fly River and delta, Papua New Guinea, nine species of oxudercine gobies (Gobiidae: Oxudercinae) were recorded: Boleophthalmus caeruleomaculatus, Oxuderces wirzi, Periophthalmodon freycineti, Periophthalmus darwini, Periophthalmus novaeguineaensis, Periophthalmus takita, Periophthalmus weberi, Scartelaos histophorus and Zappa confluentus. An exploratory multivariate analysis of their habitat conditions discriminated five guilds, differentially distributed in habitats with different quantities of environmental water and three guilds corresponding to different levels of salinity. A partial correspondence between phylogenetic and ecological categories suggested the presence of parallel adaptive radiations within different genera. In particular, the species found in the most terrestrial habitats (P. weberi) was also found in the widest range of conditions, suggesting that colonization of extreme semi-terrestrial and freshwater habitats by this species was facilitated by eurytypy. It is proposed that these findings provide insight into convergent adaptations for the vertebrate eco-evolutionary transition from sea to land.
This study provides a first description of the phylogeographic patterns and evolutionary history of two species of the mudskipper genus Periophthalmus. These amphibious gobies are distributed throughout the whole Indo-Pacific region and Atlantic coast of Africa, in peritidal habitats of soft-bottom coastal ecosystems. Three sequence datasets of two widely distributed species, Periophthalmus argentilineatus and P. kalolo, were obtained by amplifying and sequencing two mtDNA markers (D-loop and 16S rDNA) and the nDNA rag1 region. The three datasets were then used to perform phylogeographic, demographic and population genetic analyses. Our results indicate that tectonic events and past climatic oscillations strongly contributed to shape present genetic differentiation, phylogeographic and demographic patterns. We found support for the monophyly of P. kalolo, and only shallow genetic differentiation between East-African and Indo-Malayan populations of this species. However, our collections of the morphospecies P. argentilineatus include three molecularly distinct lineages, one of them more closely related to P. kalolo. The presence of Miocenic timings for the most recent common ancestors of some of these morphologically similar clades, suggests the presence of strong stabilising selection in mudskippers' habitats. At population level, demographic analyses and palaeoecological records of mangrove ecosystems suggest that Pleistocene bottlenecks and expansion plus secondary contact events of the studied species were associated with recurrent sea transgressions during interglacials, and sea regressions or stable regimes during glacials, respectively.
The relationship between acute thermal tolerance and habitat temperature in ectotherm animals informs about their thermal adaptation and is used to assess thermal safety margins and sensitivity to climate warming. We studied this relationship in an equatorial freshwater snail (Clea nigricans), belonging to a predominantly marine gastropod lineage (Neogastropoda, Buccinidae). We found that tolerance of heating and cooling exceeded average daily maximum and minimum temperatures, by roughly 20°C in each case. Because habitat temperature is generally assumed to be the main selective factor acting on the fundamental thermal niche, the discordance between thermal tolerance and environmental temperature implies trait conservation following 'in situ' environmental change, or following novel colonisation of a thermally less-variable habitat. Whereas heat tolerance could relate to an historical association with the thermally variable and extreme marine intertidal fringe zone, cold tolerance could associate with either an ancestral life at higher latitudes, or represent adaptation to cooler, higher-altitudinal, tropical lotic systems. The broad upper thermal safety margin (difference between heat tolerance and maximum environmental temperature) observed in this snail is grossly incompatible with the very narrow safety margins typically found in most terrestrial tropical ectotherms (insects and lizards), and hence with the emerging prediction that tropical ectotherms, are especially vulnerable to environmental warming. A more comprehensive understanding of climatic vulnerability of animal ectotherms thus requires greater consideration of taxonomic diversity, ecological transition and evolutionary history.
A study was conducted on the habitat distribution of four sympatric species of Periophthalmus (the silver-lined mudskipper Periophthalmus argentilineatus, the slender mudskipper Periophthalmus gracilis, the kalolo mudskipper Periophthalmus kalolo and the Malacca mudskipper Periophthalmus malaccensis) from northern Sulawesi. Molecular phylogenetic reconstructions based on one mtDNA marker (16S) were used to validate the morphological taxa, identifying five molecular clades. Periophthalmus argentilineatus includes two molecular species, which are named Periophthalmus argentilineatus clades F and K. Multivariate direct gradient analysis show that these species form three distinct ecological guilds, with the two molecular species occurring in different guilds. Periophthalmus clade F is ecologically eurytypic; Periophthalmus clade K and P. kalolo are prevalent in ecosystems isolated by strong oceanic currents and at shorter distances from the sea; P. gracilis plus P. malaccensis are prevalent in ecosystems connected by shallow coastal waters, in vegetated habitats at larger distances from the sea. This indicates for the first time that mudskipper species exhibit a range of adaptations to semiterrestrialism not only within genera, but even within morphospecies, delineating a much more complex adaptive scenario than previously assumed.
A new species of the genus Sabellaria Lamarck, 1818 (Annelida: Polychaeta: Sabellariidae) is described from the intertidal zone of Jeram, Selangor, Malaysia. Sabellaria jeramae n. sp. is a gregarious species that constructs large reefs several hundreds of meters long and 50-200 m wide. The new species is distinguished from other congeners by the character combination of the presence of a single kind of middle paleae with conspicuous morphology, and outer paleae with long frayed teeth. Morphological features of the species are described and compared to those of all congeneric species. We also compare the reef structure and geographical distribution of the new species to those of the members of the family Sabellariidae around the world, demonstrating the ecological traits of the reefs.
Coupled behavioural observations and acoustical recordings of aggressive dyadic contests showed that the mudskipper Periophthalmodon septemradiatus communicates acoustically while out of water. An analysis of intraspecific variability showed that specific acoustic components may act as tags for individual recognition, further supporting the sounds' communicative value. A correlative analysis amongst acoustical properties and video-acoustical recordings in slow-motion supported first hypotheses on the emission mechanism. Acoustic transmission through the wet exposed substrate was also discussed. These observations were used to support an "exaptation hypothesis", i.e. the maintenance of key adaptations during the first stages of water-to-land vertebrate eco-evolutionary transitions (based on eco-evolutionary and palaeontological considerations), through a comparative bioacoustic analysis of aquatic and semiterrestrial gobiid taxa. In fact, a remarkable similarity was found between mudskipper vocalisations and those emitted by gobioids and other soniferous benthonic fishes.
Salmonid species are main actors in the Italian socio-ecological landscape of inland fisheries. We present novel data on the size-age structure of one of the remnant Italian populations of the critically endangered marble trout Salmo marmoratus, which co-occurs with other stocked non-native salmonids in a large glacial river of the Lake Maggiore basin (Northern Italy-Southern Switzerland). Like other Italian native trout populations, the Toce River marble trout population is affected by anthropogenic introgression with the non-native brown trout S. trutta. Our sample includes 579 individuals, mainly collected in the Toce River main channel. We estimated the length-weight relationship, described the population size-age structure, estimated the age-specific growth trajectories, and fit an exponential mortality model. A subset of the sample was also used to measure numerical and biomass density. The estimated asymptotic maximum length is ~105 cm total length (TL). Mean length at first maturity is ~55 cm TL, and mean length at maximum yield per recruit is ~68 cm TL. Approximately 45-70% of the population are estimated to die annually, along with a fishing annual mortality of ~37%, with an exploitation ratio of ~0.5. The frequency distribution of length classes in a sample collected by angling shows that ~80% of the individuals that could be retained according to the current recreational fishing regulations likely never reproduced, and large fish disproportionally contributing to recruitment are fished and retained. We identify possible overfishing risks posed by present regulations, and propose updated harvest-slot length limits to mitigate such risks. More detailed and long-term datasets on this system are needed to more specifically inform the fishery management and monitor the effects of any change in the management strategy on the size-age structure of the marble trout population of the Toce River.