A black-and-red stick insect from the Philippines – observations on the external anatomy and natural history of a new species of Orthomeria

A new stick insect of the genus Orthomeria Kirby, 1904 (Phasmatodea, Aschiphasmatidae) is described from the Philippines. Orthomeria (Orthomeria) kangi sp. n. is readily distinguished from all other congeners by the distinctive blood red colouration of the costal region of the hind wings. Major features of the external morphology of adults, eggs, and first-instar nymphs are illustrated. Locomotory attachment pads are of the smooth type with irregular microgrooves on the contact surface. An unusual condition of male terminalia is the absence of tergal thorn pads on segment 10. The male clasping organs are represented by an elongated vomer terminating in a prominent spine, and by incurved cerci featuring a bilobed apex equipped with a sharp blade-like ridge. Intraspecific variation in body colouration and hind wing length occurs in females. The new species lives at 400-650 m elevation in the surroundings of the Sablang and Tuba regions, in the Benguet Province of Luzon island. Host plants include Ficus spp. (Moraceae), and Pipturus spp. and Leucosyke spp. (Urticaceae). Observations on the mating and defensive behaviour are presented. Orthomeria (Orthomeria) catadromus (Westwood, 1859) is recognised as a junior synonym of Orthomeria (Orthomeria) pandora (Westwood, 1859), syn. n. A lectotype is designated for both species. Finally, an updated identification key to the species of the subgenus Orthomeria is provided.     

The evolution of optimal emergence times: bet hedging and the quest for an ideal free temporal distribution of individuals

Proper timing of activities is one of the principal challenges faced by most organisms. Organisms need to account for various aspects in decision making like avoiding inordinate risks, synchronizing with resource availability, or finding mates. We provide analytical and simulation models to investigate the influence of life expectancy, resource competition and unpredictable environmental conditions (environmental uncertainty) on the evolutionarily stable distribution of emergence times in organisms depending on seasonally available resources. We focus on the partitioning of total phenotypic variance in emergence times into 1) genetic variance in mean emergence times between lineages and 2) environmental trait variance that determines the intra‐lineage variance in the timing of emergence. Both, life expectancy of organisms and intensity of competition severely influence the evolutionary response to environmental uncertainty. Our main findings can be summarized as follows: 1) in general diversifying bet hedging (environmental trait variance) is the adequate mechanism to reduce the risk arising from environmental uncertainty while conservative bet hedging, i.e. delaying emergence into ‘safe’ phases of the season is restricted to short lived organisms and to situations with vanishing competition. 2) Environmental trait variance increases with increasing environmental uncertainty whereas 3) significant genetic variance evolves only under severe resource competition; it is driven by selection for an ideal free distribution of emergence times. 4) The level of genetic variance evolving declines with increasing life expectancy of organisms. 5) With sufficiently short life expectancy evolutionary branching and coexistence of distinctly different emergence strategies occurs; the number of co‐occurring strategies is determined by the level of environmental uncertainty. Our model provides cues for understanding how different ecological factors contribute and interact to shape the evolution of emergence strategies.     

‘Stromatolites’ built by sponges and microbes – a new type of Phanerozoic bioconstruction

Two ‘stromatolites’ from Carboniferous and Triassic carbonates previously regarded as microbial bioconstructions are analysed and reinterpreted as sponge‐microbial build‐ups. The automicritic aggregations in these build‐ups are similar to the previously reported fossils of keratose demosponges in showing moulded anastomosing filamentous structures. All the studied columnar or domal constructions were formed in turbulent water with high sedimentation rate. The Carboniferous build‐ups were constructed in the shallow subtidal zone of an open shelf or a ramp. The laminations within the stromatolite‐like columns are composed of alternating dark micritic laminae of sponge fossils and pale laminae of neomorphic microspars. The accretion of these columns is probably related to the repeated cycles of sponge growth, rapid lithification after burial, re‐exposure and erosion, and settlement of new generations. The Triassic rocks are presumed to have been precipitated in a slightly evaporitic environment based on lithological features. They show a transition from planar laminae, which were formed under the influence of microbial mats, to stromatolitic columnar or domal build‐ups, which are dominated by stacked micritic clumps of probable sponge fossils. The sponge–microbe alternation may have been controlled by variation of salinity. Comparable with a recent study, this work shows that sponge‐related bioconstructions can be morphologically similar to microbialites in the level of mega‐ and mesostructures.     

Environment not dispersal limitation drives clonal composition of Arctic Daphnia in a recently deglaciated area

One of the most prominent manifestations of the ongoing climate warming is the retreat of glaciers and ice sheets around the world. Retreating glaciers result in the formation of new ponds and lakes, which are available for colonization. The gradual appearance of these new habitat patches allows us to determine to what extent the composition of asexual Daphnia (water flea) populations is affected by environmental drivers vs. dispersal limitation. Here, we used a landscape genetics approach to assess the processes structuring the clonal composition of species in the D. pulex species complex that have colonized periglacial habitats created by ice‐sheet retreat in western Greenland. We analysed 61 populations from a young (<50 years) and an old cluster (>150 years) of lakes and ponds. We identified 42 asexual clones that varied widely in spatial distribution. Beta‐diversity was higher among older than among younger systems. Lineage sorting by the environment explained 14% of the variation in clonal composition whereas the pure effect of geographical distance was very small and statistically insignificant ( = 0.010, P = 0.085). Dispersal limitation did not seem important, even among young habitat patches. The observation of several tens of clones colonizing the area combined with environmentally driven clonal composition of populations illustrates that population assembly of asexual species in the Arctic is structured by environmental gradients reflecting differences in the ecology of clones.