19 research outputs found
Sources of Variation in Growth, Form, and Survival in Dwarf and Normal-Stature Pitch Pines (Pinus rigida, Pinaceae) in Long-Term Transplant Experiments
Determining the relative contributions of genetic and environmental factors to phenotypic variation is critical for understanding the evolutionary ecology of plant species, but few studies have examined the sources of phenotypic differentiation between nearby populations of woody plants. We conducted reciprocal transplant experiments to examine sources of variation in growth rate, form, survival, and maturation in a globally rare dwarf population of pitch pine (Pinus rigida) and in surrounding populations of normal-stature pitch pines on Long Island, New York. Transplants were monitored over a 6-yr period. The influence of seedling origin on height, growth rate, survival, and form (single-stemmed vs. multi-stemmed growth habit) was much smaller than the effect of transplanting location. Both planting site and seed origin were important factors in determining time to reproduction; seedlings originating from dwarf populations and seedlings planted at the normal-stature site reproduced earliest. These results suggest that many of the differences between dwarf and normal-stature pitch pines may be due more to plastic responses to environmental factors than to genetic differentiation among populations. Therefore, preservation of the dwarf pine habitat is essential for preserving dwarf pine communities; the dwarf pines cannot be preserved ex situ
RESEARCH ARTICLE Body-size structure of Central Iberian mammal fauna reveals semidesertic conditions during the middle Miocene Global Cooling Event
We developed new quantitative palaeoclimatic inference models based on the body-size
structure of mammal faunas from the Old World tropics and applied them to the Somosaguas
fossil site (middle Miocene, central Iberian Peninsula). Twenty-six mammal species
have been described at this site, including proboscideans, ungulates, carnivores, insectivores,
lagomorphs and rodents. Our analyses were based on multivariate and bivariate
regression models correlating climatic data and body-size structure of 63 modern mammal
assemblages from Sub-Saharan Africa and the Indian subcontinent. The results showed an
average temperature of the coldest month higher than 26ÊC for the Somosaguas fossil site,
a mean annual thermal amplitude around 10ÊC, a drought length of 10 months, and an
annual total precipitation greater than 200 mm per year, which are climate conditions typical
of an ecotonal zone between the savanna and desert biomes. These results are congruent
with the aridity peaks described over the middle Aragonian of Spain and particularly in the
local biozone E, which includes Somosaguas. The aridity increase detected in this biozone
is associated with the Middle Miocene Global Cooling Event. The environment of Somosaguas
around 14 Ma was similar to the current environment in the Sahel region of North
Africa, the Horn of Africa, the boundary area between the Kalahari and the Namib in Southern
Africa, south-central Arabia, or eastern Pakistan and northwestern India. The distribution
of modern vegetation in these regions follows a complex mosaic of plant communities,
dominated by scattered xerophilous shrublands, semidesert grasslands, and vegetation
linked to seasonal watercourses and ponds.Peer reviewe