Salinity tolerance ecophysiology of Equisetum giganteum in South America: a study of 11 sites providing a natural gradient of salinity stress

In river valleys of the world's driest desert (The Atacama of South America) large stands of giant horsetail (Equisetum giganteum) are found to tolerate soil water salinity up to at least half that of seawater. The roots selectively exclude Na and take-up K in response to salinity while stomatal conductances and photochemical efficiency of Photosystem II remain unaffected

<i>Polylepis</i> woodland dynamics during the last 20,000 years

AimTo determine the palaeoecological influences of climate change and human land use on the spatial distribution patterns of Polylepis woodlands in the Andes.LocationTropical Andes above 2,900 m between 2°S and 18°S of latitude.MethodsPollen and charcoal data were gathered from 13 Andean lake sediment records and were rescaled by the maximum value in each site. The rescaled pollen data were used to estimate a mean abundance and coefficient of variation to show woodland expansions/contractions and woodland fragmentation over the last 20,000 years. The rescaled charcoal was displayed as a 200‐year moving median using 500‐year bins to infer the influence of fire on woodland dynamics at landscape scale. Pollen and charcoal were compared with speleothem, clastic flux and archaeological data to assess the influence of moisture balance, glacial activity and human impact on the spatial distribution of Polylepis woodlands.ResultsWoodland expansion and fire were correlated with precipitation changes and glacier dynamics from c. 20 to 6 kcal BP (thousands of calibrated years before present). Charcoal abundances between 20 and 12 kcal BP were less common than from 12 kcal BP to modern. However, human‐induced fires were unlikely to be the main cause of a woodland decline centred at 11 kcal BP, as woodlands recovered from 10.5 to 9.5 kcal BP (about twofold increase). Charcoal peaks analogous to those that induced the woodland decline at 11 kcal BP were commonplace post‐9.5 kcal BP but did not trigger an equivalent woodland contraction. An increase in the coefficient of variation after c. 5.5 kcal BP suggests enhanced fragmentation and coincided with the shift from logistic to exponential growth of human populations. Over the last 1,000 years, Polylepis became hyper‐fragmented with over half of sites losing Polylepis from the record and with coefficients of variation paralleling those of glacial times.Main conclusionsPolylepis woodlands formed naturally patchy woodlands, rather than a continuous vegetation belt, prior to human occupation in the Andes. The main factors controlling pre‐human woodland dynamics were precipitation and landscape heterogeneity. Human activity led to hyper‐fragmentation during the last c. 1,000 years

Multigene phylogeny of the Mustelidae: Resolving relationships, tempo and biogeographic history of a mammalian adaptive radiation

<p>Abstract</p> <p>Background</p> <p>Adaptive radiation, the evolution of ecological and phenotypic diversity from a common ancestor, is a central concept in evolutionary biology and characterizes the evolutionary histories of many groups of organisms. One such group is the Mustelidae, the most species-rich family within the mammalian order Carnivora, encompassing 59 species classified into 22 genera. Extant mustelids display extensive ecomorphological diversity, with different lineages having evolved into an array of adaptive zones, from fossorial badgers to semi-aquatic otters. Mustelids are also widely distributed, with multiple genera found on different continents. As with other groups that have undergone adaptive radiation, resolving the phylogenetic history of mustelids presents a number of challenges because ecomorphological convergence may potentially confound morphologically based phylogenetic inferences, and because adaptive radiations often include one or more periods of rapid cladogenesis that require a large amount of data to resolve.</p> <p>Results</p> <p>We constructed a nearly complete generic-level phylogeny of the Mustelidae using a data matrix comprising 22 gene segments (~12,000 base pairs) analyzed with maximum parsimony, maximum likelihood and Bayesian inference methods. We show that mustelids are consistently resolved with high nodal support into four major clades and three monotypic lineages. Using Bayesian dating techniques, we provide evidence that mustelids underwent two bursts of diversification that coincide with major paleoenvironmental and biotic changes that occurred during the Neogene and correspond with similar bursts of cladogenesis in other vertebrate groups. Biogeographical analyses indicate that most of the extant diversity of mustelids originated in Eurasia and mustelids have colonized Africa, North America and South America on multiple occasions.</p> <p>Conclusion</p> <p>Combined with information from the fossil record, our phylogenetic and dating analyses suggest that mustelid diversification may have been spurred by a combination of faunal turnover events and diversification at lower trophic levels, ultimately caused by climatically driven environmental changes. Our biogeographic analyses show Eurasia as the center of origin of mustelid diversity and that mustelids in Africa, North America and South America have been assembled over time largely via dispersal, which has important implications for understanding the ecology of mustelid communities.</p

Biogeographical Distribution of Salt Marsh Halophytes on the Coasts of the Sonoran Desert

Twenty-four species of intertidal halophytes were recorded from 15 coastal salt marshes of the Sonoran desert. The Pacific salt marshes were found to be the most diverse, with 14.4 species per marsh, while the western Gulf of California had 8.9, and the eastern Gulf, 13.7. A low species diversity was found in the northwestern Gulf due to the absence of mid- and high-zoned halophytes. High-zoned species were geographically patchier on all coasts. The species formed three elevational groups within the intertidal zone: LOW: Spartina foliosa Trin, Distichlis palmeri (Vasey), Rhizophora mangle L., Laguncularia racemosa (L.), Avicennia gerimans (L.), Salicornia bigelovii Torr., S. europaea L., and Batis maritima L.; MID: Salicornia virginica L., Suaeda californica S. Wats., laumea carnosa (Less.), Sesuvium verrucosum Raf., Limonium californicum (Boiss.1 and Cressa truxillensis H.B.K.; HIGH: Salicornia subterminalis Parish, Allenrolfea occidentalis (S. Wats.), Frankenia grandifolia Cham. and Schlect, F. palmen S. Wats., Monanthochloe littoralis Engelm., Distichlis spicata (L.), Suaeda fruticosa (L.), Atriplex barclayana (Benth.), A. canescens (Pursh) and Sporobolus virginicus (L.). Thirty additional species were recorded in the supralittoral zone.Desert Plants is published by The University of Arizona for the Boyce Thompson Southwestern Arboretum. For more information about this unique botanical journal, please email the College of Agriculture and Life Sciences Publications Office at [email protected]