Mycorrhizal status of plant species in the Chaco Serrano Woodland from central Argentina

We examined the mycorrhizal type of 128 plant species in two patches of native vegetation of the Chaco Serrano Woodland, central Argentina, the largest dry forest area in South America. Of the 128 plant species investigated (belonging to 111 genera in 53 families), 114 were colonized by arbuscular mycorrhizal fungi (AM), orchid mycorrhizal associations were present in the five terrestrial orchid species analyzed, one ectomycorrhiza was only present in Salix humboldtiana Willd., and 96 harbored a dark septate endophyte (DSE) association. Co-occurrence of AM and DSE was observed in 88 plant species. We determine morphological types of arbuscular mycorrhizal fungi (Arum, Paris, and intermediate AM structures) and report the mycorrhizal status in 106 new species, 12 of which are endemic to central Argentina and two, Aa achalensis Schltr. and Buddleja cordobensis Griseb., are declared to be vulnerable species. Root colonization in the Chaco Serrano Woodland is widespread and should be considered in revegetation programs due to the deterioration of this particular ecosystem. Considering the predominance of AM and DSE associations and the various potential benefits that these associations may bring to plant establishment, they should receive special attention in conservation and reforestation of these woodlands.     

Foraging Behavior and Coexistence of Two Sunbird Species in a Kenyan Woodland

We investigated the mechanism of coexistence of the rare Amani Sunbird (Hedydipna pallidigastra) and the widespread Collared Sunbird (H. collaris), within Brachystegia woodland in the Arabuko‐Sokoke Forest, Kenya. We compared how prey abundance and search strategies affect resource exploitation by the two species. We used foraging theory to direct our measures of feeding activities as influenced by sunbird species, tree species and foraging height. We evaluated invertebrate abundance among tree species at different heights within trees. The Collared Sunbird primarily used the understory, and the Amani Sunbird primarily used the upper‐canopy. Overall, the rate of prey attacks per flight of the Amani Sunbird was 2.8 times greater than that of the Collared Sunbird. The Amani Sunbird, however, used increased search and attack rates in the understory compared with the mid‐ and upper‐canopies, but the Collared Sunbird foraged similarly throughout all strata. We hypothesize that the increased foraging rate of the Amani in the understory reflects increased foraging costs due to interference from the Collared Sunbird in that stratum. Furthermore, the Collared Sunbird exploits rich patches by moving frequently from place to place. The Amani Sunbird forages slowly, with reduced travel rates, and with a greater number of prey captures within a patch. Arthropod density did not differ among the vegetative strata, but was higher in Brachystegia spiciformis and Hymenaea verrucosa than in six other tree species. We hypothesize that the Amani Sunbird appears dependent upon continued tall B. spiciformis trees within the canopy of the Arabuko‐Sokoke Forest.     

Movement Patterns of a Native and Non‐native Frugivore in Hawaii and Implications for Seed Dispersal

Avian frugivores historically played important roles as seed dispersers across the Hawaiian Islands, but presently, the ‘ōma‘o (Myadestes obscurus) is the only extant native frugivore in the wild on the Island of Hawaii. During recent decades, the introduced generalist Japanese White‐eye (Zosterops japonicus) has become the most common bird in Hawaii. The movements of avian frugivores largely dictate how far seeds get dispersed and into what kinds of microhabitats. This study compares the movement patterns and diet of the ‘ōma‘o to the Japanese White‐eye to understand how a native differs from a non‐native frugivore in the type and distances of seeds dispersed. Radiotelemetry was conducted on nine ‘ōma‘o and nine Japanese White‐eyes in a system of natural forest fragments (kīpuka) created by lava flows. Japanese White‐eyes disperse seeds approximately twice as far as ‘ōma‘o; during the time of gut passage, ‘ōma‘o move a mean distance of 98.1 m, and Japanese White‐eyes move 170.1–194.8 m. However, the ‘ōma‘o disperses the seeds of at least seven different native fruit species compared with two dispersed by Japanese White‐eyes. Japanese White‐eyes were found to disperse seeds smaller than 1.5 mm, whereas the ‘ōma‘o dispersed seeds up to 6 mm in diameter. Despite their ecological differences, both birds distribute certain seeds within and among kīpuka and likely facilitate primary succession of fruiting plants in the young lava matrix. However, this study suggests that if the ‘ōma‘o were extirpated, a smaller‐bodied generalist cannot entirely substitute for the ecological role played by the native frugivore.     

Patterns of ecological specialization among microbial populations in the Red Sea and diverse oligotrophic marine environments

Large swaths of the nutrient‐poor surface ocean are dominated numerically by cyanobacteria (Prochlorococcus), cyanobacterial viruses (cyanophage), and alphaproteobacteria (SAR11). How these groups thrive in the diverse physicochemical environments of different oceanic regions remains poorly understood. Comparative metagenomics can reveal adaptive responses linked to ecosystem‐specific selective pressures. The Red Sea is well‐suited for studying adaptation of pelagic‐microbes, with salinities, temperatures, and light levels at the extreme end for the surface ocean, and low nutrient concentrations, yet no metagenomic studies have been done there. The Red Sea (high salinity, high light, low N and P) compares favorably with the Mediterranean Sea (high salinity, low P), Sargasso Sea (low P), and North Pacific Subtropical Gyre (high light, low N). We quantified the relative abundance of genetic functions among Prochlorococcus, cyanophage, and SAR11 from these four regions. Gene frequencies indicate selection for phosphorus acquisition (Mediterranean/Sargasso), DNA repair and high‐light responses (Red Sea/Pacific Prochlorococcus), and osmolyte C1 oxidation (Red Sea/Mediterranean SAR11). The unexpected connection between salinity‐dependent osmolyte production and SAR11 C1 metabolism represents a potentially major coevolutionary adaptation and biogeochemical flux. Among Prochlorococcus and cyanophage, genes enriched in specific environments had ecotype distributions similar to nonenriched genes, suggesting that inter‐ecotype gene transfer is not a major source of environment‐specific adaptation. Clustering of metagenomes using gene frequencies shows similarities in populations (Red Sea with Pacific, Mediterranean with Sargasso) that belie their geographic distances. Taken together, the genetic functions enriched in specific environments indicate competitive strategies for maintaining carrying capacity in the face of physical stressors and low nutrient availability.     

Patterns and persistence of larval retention and connectivity in a marine fish metapopulation

Connectivity, the demographic linking of local populations through the dispersal of individuals, is one of the most poorly understood processes in population dynamics, yet has profound implications for conservation and harvest strategies. For marine species with pelagic larvae, direct estimation of connectivity remains logistically challenging and has mostly been limited to single snapshots in time. Here, we document seasonal and interannual patterns of larval dispersal in a metapopulation of the coral reef fish Amphiprion polymnus. A 3‐year record of larval trajectories within and among nine discrete local populations from an area of approximately 35 km was established by determining the natal origin of settled juveniles through DNA parentage analysis. We found that spatial patterns of both self‐recruitment and connectivity were remarkably consistent over time, with a low level of self‐recruitment at the scale of individual sites. Connectivity among sites was common and multidirectional in all years and was not significantly influenced by seasonal variability of predominant surface current directions. However, approximately 75% of the sampled juveniles could not be assigned to parents within the study area, indicating high levels of immigrations from sources outside the study area. The data support predictions that the magnitude and temporal stability of larval connectivity decreases significantly with increasing distance between subpopulations, but increases with the size of subpopulations. Given the considerable effort needed to directly measure larval exchange, the consistent patterns suggest snapshot parentage analyses can provide useful dispersal estimates to inform spatial management decisions.     

Movement decline across lifespan of Caenorhabditis elegans mutants in the insulin/insulin‐like signaling pathway

Research in aging biology has identified several pathways that are molecularly conserved across species that extend lifespan when mutated. The insulin/insulin‐like signaling (IIS) pathway is one of the most widely studied of these. It has been assumed that extending lifespan also extends healthspan (the period of life with minimal functional loss). However, data supporting this assumption conflict and recent evidence suggest that life extension may, in and of itself, extend the frail period. In this study, we use Caenorhabditis elegans to further probe the link between lifespan and healthspan. Using movement decline as a measure of health, we assessed healthspan across the entire lifespan in nine IIS pathway mutants. In one series of experiments, we studied healthspan in mass cultures, and in another series, we studied individuals longitudinally. We found that long‐lived mutants display prolonged mid‐life movement and do not prolong the frailty period. Lastly, we observed that early‐adulthood movement was not predictive of late‐life movement or survival, within identical phenotypes. Overall, these observations show that extending lifespan does not prolong the period of frailty. Both genotype and a stochastic component modulate aging, and movement late in life is more variable than early‐life movement.     

Local and Regional Variation in Local Frequency of Multiple Coffee Pests Across a Mosaic Landscape in Coffea arabica's Native Range

Shaded coffee has been highlighted for its potential to conserve biodiversity, and thus perhaps also a diversity of natural enemies that could control pest organisms. In southwestern Ethiopia, coffee is grown in shade both in contiguous forests and in forest patches with native trees surrounded by open fields. We hypothesized that coffee grown in contiguous forests, which is the natural habitat for coffee (Coffea arabica) and its interacting organisms, would have less pest damage due to high protection by natural enemies. We surveyed pests on coffee plants in plots within contiguous forests (10 sites) and in forest patches (21 sites). In general, the variation in number of damaged or attacked leaves by individual insect or fungal pests was larger between plants than between plots, which suggests that very local conditions or processes are important. The spatial signals were generally weak. Coffee rust and coffee blotch miner tended to have lower infestation rates in accordance with our hypothesis, while fruit flies in ripe berries were more abundant in forest patches closer to contiguous forest. Based on interviews, olive baboons showed a clear dependency on contiguous forest habitat and were regarded as a problem only in contiguous forests and forest patches close to contiguous forests. In conclusion, we found no support for a generally stronger top‐down control on coffee pests in sites within, or with connectivity to, contiguous moist afromontane forests in the native range of coffee.     

One for all and all for one: retention of colour‐unchanged old flowers increases pollinator attraction in a hermaphroditic plant

• Long‐lived flowers increase pollen transfer rates, but these entail high water and carbon maintenance costs. The retention of pollinated and reward‐free old flowers enhances pollinator visitation to young receptive flowers by increasing floral display size. This mechanism is associated with acropetal inflorescences or changes in flower colour and openness, but the retention of unchanging solitary flowers remains overlooked.
• We examined pollination‐dependent variation in floral longevity and determined stigmatic receptivity, pollen viability and pollen removal rates among flower ages in Kielmeyera regalis, a Neotropical savanna shrub. We also evaluated the effects of floral display size on pollinator visitation rates. Lastly, we determined whether old flowers are unvisited and exclusively increase pollinator attraction to young flowers through flower removal experiments.
• Regardless of pollination treatment, flowers lasted fully open with no detectable physical changes for 3 days. Over time, stigmas remained receptive but >95% of pollen was removed. Pollinator visitation significantly increased with floral display size and intermediate percentages (15–30%) of newly opened flowers. Accordingly, the retention of reward‐free and unvisited old flowers increased young flower–pollinator interaction.
• Our results reveal the importance of a prolonged floral longevity in increasing pollinator attraction toward newly opened receptive flowers without changes in flower colour and form. We conclude that the retention of pollinated, reward‐free and unvisited colour‐unchanged old flowers in K. regalis is a strategy that counteracts the water use costs associated with the maintenance of large flowers with increased mate opportunities in a pollen‐limited scenario.

     

Multilocus analyses indicate a mosaic distribution of hybrid populations in ground squirrels (genus Ictidomys)

DNA sequence data from mitochondrial cytochrome‐b (Cytb) and Y‐linked structural maintenance of chromosomes (SmcY) genes were combined with 478 nuclear loci obtained from amplified fragment length polymorphisms (AFLP) to assess the extent of hybridization and genetic spatial structure of populations in two hybridizing species of ground squirrel (Ictidomys parvidens and Ictidomys tridecemlineatus). Based on AFLP analyses of 134 individuals from 28 populations, 10 populations were identified that possessed hybrid individuals. Overall estimates of F_ST values revealed strong support for population structure in the Cytb data set; however, analyses of the SmcY gene and the AFLP data indicated ongoing gene flow between species. Pairwise F_ST comparisons of populations were not significant for the SmcY gene; although they were significant for the Cytb gene, indicating that these populations were structured and that gene flow was minimal. Therefore, gene flow between I. parvidens and I. tridecemlineatus appeared to be restricted to populations that exhibited hybridization. In addition, the fragmented nature of the geographic landscape suggested limited gene flow between populations. As a result, the distributional pattern of interspersed parental and hybrid populations were compatible with a mosaic hybrid zone model. Because ground squirrels display female philopatry and male‐biased dispersal, the ecology of these species is compatible with this hypothesis.