Biology subjects

Rull, V.

Publications and source records attributed to Rull, V..

6 recordsLinked to original sources

bioRxiv2023

A continuous centennial Lateglacial-Early Holocene (15-10 cal kyr BP) palynological record from the Iberian Pyrenees and regional comparisons

This paper presents the first continuous (gap-free) Lateglacial-Early Holocene (LGEH) pollen record for the Iberian Pyrenees resolved at centennial resolution. The main aims are (i) to provide a standard chronostratigraphic correlation framework, (ii) to unravel the relationships between vegetation shifts, climatic changes and fire, and (iii) to obtain a regional picture of LGEH vegetation for the Pyrenees and the surrounding lowlands. Seven pollen assemblage zones were obtained and correlated with the stadial/interstadial phases of the Greenland ice cores that serve as a global reference. Several well-dated datums were also derived for keystone individual taxa that are useful for correlation purposes. Four vegetation types were identified, two of them corresponding to conifer and deciduous forests (Cf, Df) and two representing open vegetation types (O1, O2) with no modern analogs, dominated by Artemisia-Poaceae and Saxifraga-Cichiroideae, respectively. Forests dominated during interstadial phases (Bolling/Allerod and Early Holocene), whereas O1 dominated during stadials (Oldest Dryas and Younger Dryas), with O2 being important only in the first half of the Younger Dryas stadial. The use of pollen-independent proxies for temperature and moisture allowed the reconstruction of paleoclimatic trends and the responses of the four vegetation types defined. The most relevant observation in this sense was the finding of wet climates during the Younger Dryas, which challenges the traditional view of arid conditions for this phase on the basis of former pollen records. Fire incidence was low until the early Holocene, when regional fires were exacerbated, probably due to the combination of higher temperatures and forest biomass accumulation. These results are compared with the pollen records available for the whole Pyrenean range and the surrounding lowlands within the framework of elevational, climatic and biogeographical gradients. Some potential future developments are suggested on the basis of the obtained results, with an emphasis on the reconsideration of the LGEH spatiotemporal moisture patterns and the comparison of the Pyrenees with other European ranges from different climatic and biogeographical regions.

paleontology↗

bioRxiv2023

A 20th-century Cannabis pollen increase in the varved record of Lake Montcortes (Iberian Pyrenees) and its potential causes

The continuous, varved and absolutely dated sedimentary record of Lake Montcortes (Iberian Pyrenees) has provided evidence for a distinct and characteristic 20th century (1980s) increase in Cannabis pollen (20C) that persists today. This event was coeval with the geographical shift of the hemp production center in the Iberian Peninsula from east to northeast (where Lake Montcortes lies), which was accompanied by a significant production increase. This increasing trend was fostered by the renewed interest of the paper industry in hemp and was promoted by the onset of European Union subsidies to hemp cultivation. Illegal cannabis crops could have also contributed to the Cannabis pollen increase, but sound evidence is still lacking. These preliminary conclusions should be reinforced by increasing the resolution of the current palynological record and modeling the dispersal of Cannabis pollen around the Montcortes region. More similar high-resolution records are needed to verify the geographical extent of the 20C event. Additionally, Lake Montcortes varved sediments are proposed as a suitable candidate to characterize the onset of the "Anthropocene" epoch (mid-20th century), as currently defined by the Anthropocene Working Group.

paleontology↗

bioRxiv2022

The Neogene-Quaternary diversification trend in the shaping of modern Caribbean mangroves

This paper analyzes the diversification of the Neotropical mangrove flora from the Miocene to the present, using a fairly comprehensive database of 110 pollen records distributed across the whole Caribbean region. A Neogene-Quaternary diversification trend (NQDT) has been identified, characterized by an increase of 25 genera (~78%) with respect to the 7 already existing Paleogene representatives. Only two genera appeared during the Miocene and the maximum increases were observed in the Pliocene-Quaternary transition and the modernliving record. Half of the true-mangrove genera (Rhizophora, Pelliciera, Acrostichum) were already present before the Neogene and the others appeared gradually in the Oligo-Miocene (Crenea), the Early-Middle Miocene (Avicennia) and the Mio-Pliocene (Laguncularia). None of the extant associate mangrove genera were present during the Paleogene and all appeared in the Miocene (23 genera) or the Oligo-Miocene transition (3 genera), being the main responsible for the NQDT, in absolute numbers. No regional extinctions were recorded since the Miocene in the Caribbean mangroves, at the generic level. These observations should be complemented with further high-resolution quantitative studies aimed at finding potential causal relationships with climatic, eustatic and paleogeographical shifts.

paleontology↗

bioRxiv2022

Taxon cycles in Neotropical mangroves

The concept of taxon cycle involves successive range expansions and contractions over time through which a species can indefinitely maintain its core distribution. Otherwise, it becomes extinct. Taxon cycles have been defined mostly for tropical island faunas, examples from continental areas are scarce and similar case studies for plants remain unknown. Most taxon cycles have been identified on the basis of phylogeographic studies, and straightforward empirical evidence from fossils is lacking. Here, empirical fossil evidence is provided for recurrent Eocene to present expansion/contraction cycles in a mangrove taxon (Pelliciera), after a Neotropical-wide study of the available pollen records. This recurrent behavior is compatible with the concept of taxon cycle from biogeographical, chronological and ecological perspectives. The biotic and abiotic drivers potentially involved in the initiation and maintenance of the Pelliciera expansion/contraction cycles are analyzed, and the ecological and evolutionary implications are discussed. Whether this could be a trend toward extinction is considered under the predictions of the taxon cycle theory. The recurrent expansion and contraction cycles identified for Pelliciera have strong potential for being the first empirically and unequivocally documented taxon cycles and likely the only taxon cycles documented to date for plants.

paleontology↗

bioRxiv2022

Historical biogeography of Cannabis in the Iberian Peninsula: palynological evidence

The tempo and mode of colonization of the Iberian Peninsula (IP) by Cannabis sativa, its further internal spreading and the potential cultural and environmental factors involved remain unknown. The available continental-wide European meta-analyses using pollen and archaeological evidence account for only a few IP sites, insufficient for a sound assessment. This paper presents a nearly comprehensive database of almost 60 IP sites with palynological evidence of Cannabis and analyzes the corresponding spatiotemporal patterns. The first scattered records of this pollen type, likely corresponding to wild Cannabis, date from the Middle and Upper Paleolithic (150 to 12 ky BP) and would have entered the IP by maritime Mediterranean or terrestrial continental pathways, or both. A first burst of introductions, probably in a cultivated form, would have occurred during the Neolithic (7-5 ky BP) using similar paths. Human participation in this Neolithic acceleration remains unclear but cannot be dismissed. A period of reduced Cannabis arrivals (mostly via MP) occurred between the Chalcolithic and the Roman Epoch (4.5-2 ky BP), when the innermost parts of the IP were colonized (Late Bronze). A second, likely anthropogenic, introduction acceleration took place in the Middle Ages (1.5 ky BP onward) using the MP and CP. Maximum cultivation and hemp retting activity was recorded during the Modern Ages (16th-19th centuries), coinciding with the increased demand of hemp fiber to supply the Spanish royal navy for imperial expansion and commerce. A potential link between Cannabis colonization/introduction bursts and climatic warmings has been observed that should be tested with future studies. Regional moisture variations seem to be less influential. Further efforts to enhance and improve the database used in this study are encouraged. The results of this paper should be compared with archaeological and historical evidence to clarify the role of human migrations and cultural changes in the historical biogeography of Cannabis in the IP.

paleontology↗

bioRxiv2022

Bacterial phylogenetic markers in lake sediments as evidence for historical hemp retting

Documenting prehistoric and historical hemp retting for fiber extraction is important in the study of human uses of this iconic plant and its cultural implications. In paleoecology, hemp retting is usually inferred from indirect proxies, notably anomalously high percentages of Cannabis pollen in lake sediments, but some recent studies have also used specific molecular biomarkers (cannabinol, Cannabis DNA) as a more straightforward evidence. Here we provide direct evidence of hemp retting by identifying phylogenetic signatures (16S rRNA genes) from pectinolytic bacteria actually responsible for the fermentation process that separates the fiber from the stalk, namely Bacillus, Clostridium, Escherichia, Massilia, Methylobacterium, Pseusomonas, Rhizobium and Rhodobacter. These analyses have been performed in the sediments from an Iberian lake previously considered as an important hemp retting site during the last five centuries, on the basis of Cannabis pollen abundances. The good match between biomarker and pollen evidence, in the context of the recent historical development of hemp industry in Spain, can be useful to interpret paleoecological records from other similar lakes in the way toward a more regional view on the introduction, spreading, uses and associated cultural connotations of Cannabis in the Iberian Peninsula within European and Mediterranean contexts.

paleontology↗