A complex species complex: The controversial role of ecology and biogeography in the evolutionary history of Syllis gracilis Grube, 1840 (Annelida,Syllidae)

The cryptic diversity in the polychaete Syllis gracilis Grube, 1840, in the Mediterranean Sea was examined with an integrative morpho-molecular approach. Individuals of S. gracilis were collected at eleven Mediterranean localities to provide an insight into the role of brackish environments in inducing cryptic speciation. The examination of morphological features combined with a molecular genetic analysis based on a partial sequence of the 16S rRNA gene highlighted discrepancies between morphological and molecular diversity. Morphological data allowed to identify a morphotype with short appendages occurring in coralline algae communities and another one with long appendages observed in brackish-water environments and Sabellaria reefs. Multivariate analyses showed that sampling localities were the greatest source of morphological divergence, suggesting that phenotypic plasticity may play a role in local adaptations of S. gracilis populations. Molecular data showed the occurrence of four divergent lineages not corresponding to morphological clusters. Different species delimitation tests gave conflicting results, retrieving, however, at least four separated entities. Some lineages occurred in sympatry and were equally distributed in marine and brackish-water environments, excluding a biogeographic or ecological explanation of the observed pattern and suggesting instead ancient separation between lineages and secondary contact. The co-occurrence of different lineages hindered the identification of the lineage corresponding to S. gracilis sensu stricto. The discrepancy between morphological and molecular diversity suggests that different environmental and biogeographic features may interact in a complex and unpredictable way in shaping diversity patterns. An integrative approach is needed to provide a satisfactory insight on evolutionary processes in marine invertebrates.     

Origins and patterns of endemic diversity in two specialized lizard lineages from the Australian Monsoonal Tropics (Oedura spp.)

Aim

Savanna biomes cover around 20% of land surfaces, yet the origins and processes that have shaped their biodiversity remain understudied. Here, we assess the timing of diversification and how patterns of genetic diversity vary along an aridity gradient in specialized saxicoline gecko clades (Oedura spp.) from the tropical savannas of northern Australia.

Location

Australian Monsoonal Tropics (AMT), Kimberley region (Western Australia).

Methods

We compiled mitochondrial and nuclear data for two Kimberley endemic lizard clades (Oedura filicipoda/murrumanu and O. gracilis), and allied non‐Kimberley taxa (O. marmorata complex). Species delimitation methods were used to identify evolutionary lineages, Maximum‐likelihood and Bayesian phylogenetic methods were employed to assess relationships and diversification timeframes, and rainfall data and range sizes were tested for correlations.

Results

Phylogenetic analyses of cryptic or recently discovered lineage diversity revealed late‐Miocene to early‐Pliocene crown ages. Microendemism and diversity were highest in high‐rainfall regions, while the most widespread lineages occurred in the central and south‐east Kimberley, and showed evidence of introgression with parapatric lineages.

Main conclusions

The initial diversification in both clades was broadly concordant with global climatic events linked to the expansion of savanna biomes in the lateMiocene. Higher endemism in mesic and refugial areas suggests long histories of localized persistence, while wider distributions and evidence of introgression suggest a dynamic history at the arid‐monsoonal interface.     

Reprogramming of Stem Cell Activity to Convert Thorns into Branches

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Unravelling the coordination between leaf and stem economics spectra through local and global scale approaches

The existence of a coordination between leaf and stem economic spectra in woody species has been postulated repeatedly in the literature, with contrasting results. Here, we postulated that this coordination is conditioned by climate factors, being stronger in stressful environments. To test this hypothesis we explored the coordination between leaf and stem economic spectra in a seasonally dry forest in central Argentina and at the global scale, we analysed if the outcome of their coordination varies along a climatic gradient. At the local scale, we characterized leaf and stem economic spectra in 37 woody species by measuring six leaf and stem functional traits related to resource acquisition and use, and two functional traits used as proxies of water transport and use capacities. At the global scale, a meta‐regression was performed to analyse if the outcome of the coordination among leaf and stem traits varies along gradients of the mean precipitation of the driest quarter and of the minimum temperature of the coldest month. At the local scale, we observed a high integration among the measured leaf and stem traits, and this coordination seemed to be linked to hydraulic properties. At the global scale, we found not only that the overall weighted mean effect size of the correlation between specific leaf area and wood density was significant and negative but also that the coordination between leaf and stem traits seemed to be shaped by climate and tends to become stronger under harsh climate conditions. Furthermore, although our results seem to suggest that their coordination is context‐dependent, alternative strategies could be observed under stressful conditions.     

Genetic and allelopathic differences between populations of daisy fleabane Erigeron annuus (L.) Pers. (Asteraceae) from disturbed and stable habitats

The interactions between invasive plants and their habitats may vary at different phases of the invasion process and depend on the phenotypic plasticity or local adaptations of each species. In this study, we investigated whether habitat changes during the invasion process are related to variations in the physiological traits (allelopathic properties) and genetic differentiation of daisy fleabane (Erigeron annuus (L.) Pers.). E. annuus is a winter annual invasive species that originated in North America and is now distributed throughout Europe. Genetic and genotypic diversity analyses were performed for 37 populations of E. annuus based on inter simple sequence repeat (ISSR) polymorphisms. In total, 684 plants were analyzed; 342 were from stable habitats and 342 were from disturbed habitats. The genetic differences among the populations from the different habitats were studied using a Bayesian cluster analysis and an analysis of molecular variance (AMOVA) and by calculating the genetic and genotypic diversity parameters. A germination test using the juglone index was employed to examine the potential allelopathic properties of the plants from the different habitats. Bayesian cluster analysis, AMOVA and allelopathic effects evaluation revealed differences in the allelopathic potential and genetic structure of the E. annuus populations from the disturbed and stable habitats. This differentiation of populations could be associated with founder effects or with different selection pressures among habitats.     

A sublethal effect on native Anthocoris nemoralis through competitive interactions with invasive Harmonia axyridis

1. The invasive ladybird Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is implicated in declines of native ladybirds with intraguild predation identified as an underlying mechanism, however, less studied are the effects on non‐coccinellid predators. Intraguild predation between Anthocoris nemoralis Fabricius (Heteroptera: Anthocoridae) and H. axyridis and the relative effects of inter‐ and intraspecific competition on predators on potted Tilia cordata Mill. was investigated, at two aphid densities. 2. Intraguild predation was unidirectional in favour of H. axyridis in Petri dishes although a low level of ladybird egg predation by A. nemoralis occurred. However, on trees intraguild predation was rare. 3. A positive effect of aphid density on H. axyridis weight gain, and increased survival when reared with A. nemoralis on potted trees indicated stronger effects of intraspecific competition on H. axyridis. Consistent suppression of aphids by ladybirds revealed their superior competition for aphids. 4. Anthocoris nemoralis weight gain was reduced when reared with H. axyridis on potted trees, indicating a potential for a sublethal effect through interspecific competition. Survivorship of A. nemoralis did not differ between con‐ and heterospecific treatments, but high aphid density enhanced A. nemoralis survival. Overall, high mortality among nymphs across treatments suggested effects related to both inter‐ and intraspecific competition for resources. 5. Results provide evidence of a sublethal effect by invasive H. axyridis through resource competition, suggesting that where these predators co‐occur, competitive interactions for shared prey are more likely to affect A. nemoralis populations than intraguild predation by H. axyridis.