Strategies of diaspore dispersal investment in Compositae: the case of the Andean highlands.

BACKGROUND AND AIMS: Understanding diaspore morphology and how much a species invests on dispersal appendages is key for improving our knowledge of dispersal in fragmented habitats. We investigate diaspore morphological traits in high-Andean Compositae and their main abiotic and biotic drivers and test whether they play a role in species distribution patterns across the naturally fragmented high-Andean grasslands. METHODS: We collected diaspore trait data for 125 Compositae species across 47 tropical high-Andean summits, focusing on achene length and pappus-to-achene length ratio, with the latter as a proxy of dispersal investment. We analysed the role of abiotic (temperature, elevation and latitude) and biotic factors (phylogenetic signal and differences between tribes) on diaspore traits and whether they are related to distribution patterns across the Andes, using phylogenomics, distribution modelling and community ecology analyses. KEY RESULTS: Seventy-five percent of the studied species show small achenes (length <3.3 mm) and 67% have high dispersal investment (pappus length at least two times the achene length). Dispersal investment increases with elevation, possibly to compensate for lower air density, and achene length increases towards the equator, where non-seasonal climate prevails. Diaspore traits show significant phylogenetic signal, and higher dispersal investment is observed in Gnaphalieae, Astereae and Senecioneae, which together represent 72% of our species. High-Andean-restricted species found across the tropical Andes have, on average, the pappus four times longer than the achene, a significantly higher dispersal investment than species present only in the northern Andes or only in the central Andes. CONCLUSIONS: Small achenes and high diaspore dispersal investment dominate among high-Andean Compositae, traits typical of mostly three tribes of African origin; but traits are also correlated with the environmental gradients within the high-Andean grasslands. Our results also suggest that diaspore dispersal investment is likely to shape species distribution patterns in naturally fragmented habitats.

Freeze-thaw revival of rotifers and algae in a desiccated, high-elevation (5500 meters) microbial mat, high Andes, Perú.

This is the first study of the highest elevation cyanobacteria-dominated microbial mat yet described. The desiccated mat was sampled in 2010 from an ephemeral rock pool at 5500 m above sea level in the Cordillera Vilcanota of southern Perú. After being frozen for 6 years at -20 °C in the lab, pieces of the mat were sequenced to fully characterize both the 16 and 18S microbial communities and experiments were conducted to determine if organisms in the mat could revive and become active under the extreme freeze-thaw conditions that these mats experience in the field. Sequencing revealed an unexpectedly diverse, multi-trophic microbial community with 16S OTU richness comparable to similar, seasonally desiccated mats from the Dry Valleys of Antarctica and low elevation sites in the Atacama Desert region. The bacterial community of the mat was dominated by phototrophs in the Cyanobacteria (Nostoc) and the Rhodospirillales, whereas the eukaryotic community was dominated by predators such as bdelloid rotifers (Philodinidae). Microcosm experiments showed that bdelloid rotifers in the mat were able to come out of dormancy and actively forage even under realistic field conditions (diurnal temperature fluctuations of -12 °C at night to + 27 °C during the day), and after being frozen for 6 years. Our results broaden our understanding of the diversity of life in periodically desiccated, high-elevation habitats and demonstrate that extreme freeze-thaw cycles per se are not a major factor limiting the development of at least some members of these unique microbial mat systems.

Long-term monitoring of tropical alpine habitat change, Andean anurans, and chytrid fungus in the Cordillera Vilcanota, Peru: Results from a decade of study.

The Cordillera Vilcanota in southern Peru is the second largest glacierized range in the tropics and home to one of the largest high-alpine lakes, Sibinacocha (4,860 m). Here, Telmatobius marmoratus (marbled water frog), Rhinella spinulosa (Andean toad), and Pleurodema marmoratum (marbled four-eyed frog) have expanded their range vertically within the past century to inhabit newly formed ponds created by ongoing deglaciation. These anuran populations, geographically among the highest (5,200-5,400 m) recorded globally, are being impacted by the chytrid fungus Batrachochytrium dendrobatidis (Bd), and the disease it causes, chytridiomycosis. In this study, we report results from over a decade of monitoring these three anuran species, their habitat, and Bd infection status. Our observations reveal dynamic changes in habitat including ongoing rapid deglaciation (18.4 m/year widening of a corridor between retreating glaciers from 2005 to 2015), new pond formation, changes in vegetation in amphibian habitat, and widespread occurrence of Bd in amphibians in seven sites. Three of these sites have tested positive for Bd over a 9- to 12-year period. In addition, we observed a widespread reduction in T. marmoratus encounters in the Vilcanota in 2008, 2009, and 2012, while encounters increased in 2013 and 2015. Despite the rapid and dynamic changes in habitat under a warming climate, continued presence of Bd in the environment for over a decade, and a reduction in one of three anuran species, we document that these anurans continue to breed and survive in this high Andean environment. High variability in anuran encounters across sites and plasticity in these populations across habitats, sites, and years are all factors that could favor repopulation postdecline. Preserving the connectivity of wetlands in the Cordillera Vilcanota is therefore essential in ensuring that anurans continue to breed and adapt as climate change continues to reshape the environment.