Vegetation assemblages of central Mexico through the late Quaternary: modern analogs and compositional turnover

Abstract

Question When did vegetation assemblages that occupy modern central Mexico appear within the context of the late Quaternary? Location Central Mexico. Methods We used modern and fossil pollen data sets from central Mexico to explore the evolution of regional vegetation through the late Quaternary. A total of 1397 samples (1357 fossil samples distributed in 17 records and 40 modern samples) were analysed through detrended correspondence analysis to evaluate the degree of analogy between modern and past vegetation assemblages, and regional vegetation compositional turnover through time. Results There was a high degree of analogy between modern and glacial vegetation, whereas the early and mid‐Holocene were characterized by a high frequency of no‐modern‐analogue pollen assemblages. Vegetation turnover during the glacial time was characterized by both pulses of abrupt change and episodes of stability. In contrast, vegetation turnover was high through most of the Holocene. Both vegetation turnover and past vegetation analogy to modern were not synchronous in altitudinal zones, except for the past 2000 yrs, when pollen assemblages suggest a high vegetation analogy to modern‐day throughout the region. Conclusions Human impacts on central Mexico regional vegetation were consistently evident during the last 2000 yrs, suggesting that biodiversity expressed in the modern vegetation assemblages incorporates a high anthropogenic imprint. High resemblance of glacial and modern landscapes suggests that the effect of human occupation on the landscape is similar to that exerted by glacial time environmental stress. However, loss of ecosystem connectivity under the modern pattern of landscape homogenization represents an unprecedented threat for regional biodiversity.

Long‐term in situ persistence of biodiversity in tropical sky islands revealed by landscape genomics

“…The modelled lower elevations of TMVB timberline–alpine grasslands during the LGM (Figure c) is congruent with fossil pollen records down to 2,300–2,500 masl for reduced forests (similar to open forests close to the timberline) and grasslands (Caballero‐Rodríguez, Lozano‐García, & Correa‐Metrio, ; Lozano‐García & Ortega‐Guerrero, , ; Lozano‐García, Sosa‐Nájera, Sugiura, & Caballero, ). Moraines also reveal that snow lines dropped by approximately 1,000 m during glacial periods (Lozano‐García & Vázquez‐Selem, ; Vázquez‐Selem & Heine, ).…”

“…similar to open forests close to the timberline) and grasslands(Caballero- Rodr ıguez, Lozano-Garc ıa, & Correa-Metrio, 2017;Lozano-Garc ıa & Ortega-Guerrero, 1994, 1998Lozano-Garc ıa, Sosa-N ajera, Sugiura, & Caballero, 2005). Moraines also reveal that snow lines dropped by approximately 1,000 m during glacial periods (Lozano-Garc ıa & V azquez-Selem, 2005; V azquez-Selem & Heine, 2011).…”

The human impact imprint on modern pollen spectra of the Maya lands

“…Therefore, is probably the result of cosmopolitan taxa (e.g., Amaranthaceae, Ambrosia, Asteraceae, and Poaceae) acting as a gravity center of the ordination and therefore representing the transition between contrasting environments, in this case from lowlands to highlands ( Figure 3C). Indeed, this transition zone likely reflects a simplifying effect of people on the landscape (Caballero-Rodríguez et al, 2017), explaining the changes from complex tropical ecosystems to most simple temperate ecosystems in terms of its structure. On quadrants II and III of the DCA, Axis 2 produces a clear separation of lowland systems into TEF (negative scores) and TSF (positive scores) ( Figure 3D), implying a seasonality gradient previ-DISCUSSION ously reported for the region (Correa-Metrio et al, 2011;Correa-Metrio et al, 2012a).…”

Climate risk on two vegetation axes—Tropical wet‐to‐dry and temperate arid‐to‐moist forests

“…Studying these zones to understand how species react or adapt to such limits, as well as identifying those segments of a population with resistance to extreme conditions (sensu Matyas, ), would be very informative and could help us mitigate forest mortality. Humans and climate have been provoking changes in vegetation distribution for centuries, if not millennia (Caballero‐Rodriguez, Lozano‐Garcia, & Correa‐Metrio, ; Correa‐Metrio, Bush, Lozano‐Garcia, & Sosa‐Najera, ), but in the face of extensive habitat fragmentation (Aguilar‐Santelises & del Castillo, ; Asbjornsen, Ashton, Vogt, & Palacios, ; Watson, ), having a more spatially explicit hypothesis of where climate exposure is likely to have the greatest impacts on existing patterns of vegetation could direct management efforts.…”