Abstract. Close coupling of Iberian hydroclimate and North Atlantic sea
surface temperature (SST) during recent glacial periods has been identified
through the analysis of marine sediment and pollen grains co-deposited on the
Portuguese continental margin. While offering precisely correlatable records,
these time series have lacked a directly dated, site-specific record of
continental Iberian climate spanning multiple glacial cycles as a point of
comparison. Here we present a high-resolution, multi-proxy (growth dynamics
and
δ13C, δ18O, and δ234U
values) composite stalagmite record of hydroclimate from two caves in western
Portugal across the majority of the last two glacial cycles (∼220 ka).
At orbital and millennial scales, stalagmite-based proxies for hydroclimate
proxies covaried with SST, with elevated δ13C,
δ18O, and δ234U values and/or growth hiatuses
indicating reduced effective moisture coincident with periods of lowered SST
during major ice-rafted debris events, in agreement with changes in
palynological reconstructions of continental climate. While in many cases the
Portuguese stalagmite record can be scaled to SST, in some intervals the
magnitudes of stalagmite isotopic shifts, and possibly hydroclimate, appear
to have been somewhat decoupled from SST.
The range of a species is determined by the balance of its demographic rates across space. Population growth rates are widely hypothesized to be greatest at the geographic center of the species range, but indirect empirical support for this pattern using abundance as a proxy has been mixed, and demographic rates are rarely quantified on a large spatial scale. Therefore, the texture of how demographic rates of a species vary over its range remains an open question. We quantified seasonal fecundity of populations spanning the majority of the global range of a single species, the saltmarsh sparrow (Ammodramus caudacutus), which demonstrates a peak of abundance at the geographic center of its range. We used a novel, population projection method to estimate seasonal fecundity inclusive of seasonal and spatial variation in life history traits that contribute to seasonal fecundity. We replicated our study over 3 years, and compared seasonal fecundity to latitude and distance among plots. We observed large-scale patterns in some life history traits that contribute to seasonal fecundity, such as an increase in clutch size with latitude. However, we observed no relationship between latitude and seasonal fecundity. Instead, fecundity varied greatly among plots separated by as little as 1 km. Our results do not support the hypothesis that demographic rates are highest at the geographic and abundance center of a species range, but rather they suggest that local drivers strongly influence saltmarsh sparrow fecundity across their global range.
34Close coupling of Iberian hydroclimate and North Atlantic sea surface temperature (SST) 35 during recent glacial periods has been identified through the analysis of marine sediment and 36 pollen grains co-deposited on the Portuguese continental margin. These reconstructions have 37
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