Socorro Lozano-García

Distribution and Ecology of Parent Taxa of Pollen Lodged Within the Latin American Pollen Database.

The cornerstone of palaeoecological research, concerned with vegetation dynamics over the recent geological past, is a good understanding of the present-day ecology and distribution of the taxa. This is particularly necessary in areas of high floral diversity such as Latin America. Vegetation reconstructions, based on numerous pollen records, now exist with respect to all major vegetation associations from Latin America. With this ever-increasing number of sedimentary records becoming available, there is a need to collate this information and to provide information concerning ecology and distribution of the taxa concerned. The existing Latin American Pollen Database (LAPD) meets the first of these needs. Information concerning the ecology and distribution of the parent taxa responsible for producing the pollen, presently lodged within the LAPD, is the focus of this paper. The ‘dictionary’ describes the ecology and distribution of the parent taxa responsible for producing pollen identified within sedimentary records. These descriptions are based on a wide range of literature and extensive discussions with members of the palaeoecological community working in different parts of Latin America investigating a range of different vegetation types.

Distribution and ecology of parent taxa of pollen lodged within the Latin American Pollen Database

The cornerstone of palaeoecological research, concerned with vegetation dynamics over the recent geological past, is a good understanding of the present-day ecology and distribution of the taxa. This is particularly necessary in areas of high floral diversity such as Latin America. Vegetation reconstructions, based on numerous pollen records, now exist with respect to all major vegetation associations from Latin America. With this ever-increasing number of sedimentary records becoming available, there is a need to collate this information and to provide information concerning ecology and distribution of the taxa concerned. The existing Latin American Pollen Database (LAPD) meets the first of these needs. Information concerning the ecology and distribution of the parent taxa responsible for producing the pollen, presently lodged within the LAPD, is the focus of this paper. The ‘dictionary’ describes the ecology and distribution of the parent taxa responsible for producing pollen identified within sedimentary records. These descriptions are based on a wide range of literature and extensive discussions with members of the palaeoecological community working in different parts of Latin America investigating a range of different vegetation types.

Holocene Vegetation and Climate Variability in the Americas

Publisher Summary The feature of Holocene climate that changes along the Pole-Equator-Pole: Americas transect is both hemispheres were generally warmer and drier in the early, and middle Holocene. In North America, the northwestern and southeastern parts of the continent were warmer, and drier because of increased insolation, and strengthening of both the Bermuda High, and the Eastern Pacific Subtropical High. However, the heat low in the midcontinent strengthened the monsoon in the southwestern United States. In the the basin of Mexico, and southwestern United States, seasonality of precipitation was enhanced. Wetter conditions also existed in a band from Texas to the eastern Midwest. Northeast Canada, which was still covered by the Laurentide ice sheet, was the exception to an early Holocene thermal maximum. During the early, and middle Holocene, westerly storm tracks were more tightly focused than they are today between 45° and 50 ° S. Holocene climate change in the Amazon tropical rain forest was relatively minor. A reduced north south migration of the Intertropical Convergence Zone (ITCZ) during the early to middle Holocene is a possible explanation for the synchrony of maximum aridity in the two hemispheres. The mean position of the ITCZ must also have remained more northerly year-round in the early to middle Holocene, reducing easterly moisture throughout South America. Throughout the Americas, the late Holocene was generally wetter, and cooler.

Millennial-Scale Temperature Change Velocity in the Continental Northern Neotropics

Climate has been inherently linked to global diversity patterns, and yet no empirical data are available to put modern climate change into a millennial-scale context. High tropical species diversity has been linked to slow rates of climate change during the Quaternary, an assumption that lacks an empirical foundation. Thus, there is the need for quantifying the velocity at which the bioclimatic space changed during the Quaternary in the tropics. Here we present rates of climate change for the late Pleistocene and Holocene from Mexico and Guatemala. An extensive modern pollen survey and fossil pollen data from two long sedimentary records (30,000 and 86,000 years for highlands and lowlands, respectively) were used to estimate past temperatures. Derived temperature profiles show a parallel long-term trend and a similar cooling during the Last Glacial Maximum in the Guatemalan lowlands and the Mexican highlands. Temperature estimates and digital elevation models were used to calculate the velocity of isotherm displacement (temperature change velocity) for the time period contained in each record. Our analyses showed that temperature change velocities in Mesoamerica during the late Quaternary were at least four times slower than values reported for the last 50 years, but also at least twice as fast as those obtained from recent models. Our data demonstrate that, given extremely high temperature change velocities, species survival must have relied on either microrefugial populations or persistence of suppressed individuals. Contrary to the usual expectation of stable climates being associated with high diversity, our results suggest that Quaternary tropical diversity was probably maintained by centennial-scale oscillatory climatic variability that forestalled competitive exclusion. As humans have simplified modern landscapes, thereby removing potential microrefugia, and climate change is occurring monotonically at a very high velocity, extinction risk for tropical species is higher than at any time in the last 86,000 years.