Similarities between invaders and native species: Moving past Darwin's naturalization conundrum

Darwin's naturalization conundrum states that successful invaders must be closely related to native species to possess the traits to tolerate that environment, but distantly related enough to possess traits allowing exploitation of underutilized niches, thereby minimizing competition. Although influential, this hypothesis is based on several simplistic assumptions. In particular, the relationship among phylogenetic relatedness, similarity, and competition is more complex than assumed and changes with spatial and phylogenetic scale. Competitive interactions are determined by limiting similarity and trait hierarchies associated with separate traits. Successful invaders thus need to be similar to native species in some respects, but different in others. This combination of similarities and differences is unlikely to be conserved. Further, many invasive species are represented in their novel range by genotypes with extreme trait values or plasticity relative to the species mean. Selection for these genotypes may alter the similarity between invasive and native species, thus obscuring the relationship between competition and phylogenetic relatedness. As environmental filtering and competition often act on different spatial scales, approaches assessing how individual traits relate to invasion at these scales (species pools vs local community) may improve our understanding of the relationship between similarity and invasion.     

Speciation and periodic restricted environments. The case of genus Ononis L. (subsections Natrix and Viscosae)

The morpho–environmental similarity between subsections Natrix and Viscosae has been pointed out as the reason for the genetic complexity of these groups of taxa. Based on this characterization a question emerges: could a very recent ongoing evolutionary process explain that morpho–environmental similarity? ISSR and cpSSR amplifications for 45 specimens belonging to taxa of Natrix and Viscosae subsections were developed, along their biogeographic distribution areas. Twenty-nine haplotypes were detected in the biogeographic area of both subsections, 79% were exclusive haplotypes, but the rest is shared between subsections Natrix and Viscosae species. Could that haplotype sharing be the result of potential hybridization between these taxa? Do current environmental conditions restrict the gene flow among taxa? The combination of ancestral genetic polymorphism, introgression, coalescence processes and periodic restricted environments (PRE) by glacial–interglacial environmental dynamics were discussed to explain the relevant percentage of exclusive haplotypes detected, as well as the persistence of shared haplotypes. These results are in accordance with the morpho–environmental proximity previously described for both subsections.     

Diversity and host associations of dipteran insects exploiting fungal fruiting bodies in Hokuriku,central Japan

To clarify the diversity and host associations of dipteran insects exploiting fungal fruiting bodies, we collected fruiting bodies at 18 localities in Hokuriku region, central Japan, from 2012 to 2015 and examined them for the emergence of insects. In total, 14,107 dipteran individuals belonging to 20 families emerged from fungi of 8 orders, 25 families, 49 genera and 129 species. Approximately 79% of dipteran individuals belonged to three families, Phoridae, Muscidae and Drosophilidae. The faunal similarity at the family level was relatively high between central (warm‐temperate) and northern (cool‐temperate) areas of Japan. However, the species composition of Drosophilidae was much different between central and northern Japan. The difference in the species composition was discussed in relation to the climatic conditions and fungal flora. None of the species from Drosophilidae, Phoridae, Muscidae, Mycetophilidae, Lonchaeidae and Chloropidae were specialists (they exploited more than one species of fungi), but they showed differences their fungi preference. Adults of some families, especially Drosophilidae, were frequently collected from fruiting bodies, but those of other families were seldom collected, probably reflecting differences in adult feeding ecology.     

Trait‐based approach confirms the importance of propagule limitation and assembly rules in old‐field restoration

Community assembly theory is suggested as a guiding principle for ecological restoration to help understand the mechanisms that structure biological communities and identify where restoration interventions are needed. We studied three hypotheses related to propagule limitation, stress‐dominance, and limiting similarity concepts in community assembly in a restoration field experiment with a trait‐based null model approach. The experiment aimed to assist the recovery of sand grassland on former arable land in the Kiskunság, Pannonian biogeographic region, Europe. Treatments included initial seeding of five grassland species, carbon amendment, low‐intensity mowing, and combinations in 1 m by 1 m plots in three old fields from 2003 to 2008. The distribution of 10 individual plant traits was compared to the null model and the effect of time and treatments were tested with linear mixed effect models. Initial seeding had the most visible impact on species and trait composition confirming propagule limitation in grassland recovery. Reducing nutrient availability through carbon amendment strengthened trait convergence for length of flowering as expected based on the stress‐dominance hypothesis. Mowing changed trait divergence to convergence for plant height with a strengthening impact with time, supporting our hypothesis of increasing dominance of limiting similarity with time. Our results support the idea that community assembly is simultaneously influenced by propagule limitation and multiple trait‐based processes that act through different traits. The limited impact of manipulating environmental filtering and limiting similarity compared to seeding, however, supports the view that only targeting the dispersal and environmental filters in parallel would improve restoration outcome.     

东北地区6所高校校园种子植物属级相似性分析

校园植物能反映校园植物多样性水平。为了研究东北地区高校校园种子植物属组成的相似性,本研究以沈阳农业大学等6所位于东北地区的高校中的校园种子植物为研究对象,并选取北方极为常见的两个科：菊科（Asteraceae）和蔷薇科（Rosaceae）,研究其属组成的差异性与相似性。结果表明,6所高校校园种子植物属间相似性较高。菊科属的组成在各高校间差异性显著,蔷薇科属的组成在各高校相似性高。校园植物种类的多样性与差异性与校园面积、校园所处位置相关。本研究旨在为东北乃至其他地区高校校园生物多样性的进一步研究和其他高校校园植物调查提供基础。     

Comparative analysis of the dynamics of human postural control during fixation and pursuit of a visual target

The properties of the system maintaining the upright posture were compared in different states of the oculomotor system: during target fixation and horizontal fast and slow pursuit (0.1 and 0.01 Hz), recording the trajectories of the center of pressure in the frontal and the sagittal planes. Methods of nonlinear analysis were applied to assess the similarity in pairwise comparisons. The overall similarity of the frontal plane dynamics proved to be higher than that of the sagittal plane dynamics. However, differences were revealed in fast pursuit versus slow pursuit or fixation in the frontal but not in the sagittal plane. Such differences may reflect the different inertia of the oculomotor and the balance control systems. In general, the results are consistent with the current notions on the two orthogonal subsystems of postural control.     

Species Dynamics During Early Secondary Forest Succession: Recruitment, Mortality and Species Turnover

The "Initial Floristic Composition" hypothesis is applied to secondary tropical rain forest succession in abandoned agricultural fields with light previous land-use and close to seed sources. This hypothesis predicts that both pioneer and shade-tolerant species colonize a site directly after abandonment, and as the canopy closes, the recruitment of pioneers sharply declines, while recruitment of shade-tolerant species continues. It also predicts higher mortality among pioneers. Consequently, recruited and dead trees are expected to differ in species composition, with highest species richness for the recruits. During 18 mo, we monitored recruitment and mortality of trees with height ≥ 1.5 m in eight plots in abandoned cornfields with initial fallow age of 1–5 yr, in SE Mexico. Shade-tolerant species established in the first years of succession, albeit in low numbers. As predicted, recruited and dead trees differed in species richness and composition, and in shade-tolerant frequency. In contrast to our expectations, over 50 percent of recruits were from pioneer species, as high stand-level mortality opened new opportunities for continued pioneer colonization. Species turnover starts very early in succession but is not always a gradual and continuous process, complicating prevailing succession models. The strong spatial and temporal variability of succession emphasizes the need to monitor these dynamics in permanent plots across a range of initial stand ages, with multiple plots in a given age class.