Native versus non‐native invasions: similarities and differences in the biodiversity impacts of Pinus contorta in introduced and native ranges

Abstract

Aim To determine whether one of the most invasive pine species introduced to the Southern Hemisphere, Pinus contorta, has changed plant species richness, composition, diversity, and litter depth where it has invaded into native open forest, shrub steppe and grassland communities and to assess whether changes were similar in its native and introduced ranges.Location R ıo Negro Province, Argentina; Ays en and Araucan ıa Regions, Chile; Greater Yellowstone Ecosystem, USA. MethodsWe measured changes in plant species richness, species composition and cover, diversity, and litter depth associated with increasing P. contorta tree cover along the invasion front at three sites in the introduced range (Argentina and Chile) and one in the native range (Montana, USA).Results Plant species richness and cover generally declined with increasing P. contorta canopy cover, at similar rates in both the introduced and native ranges. However, plant cover was not affected by P. contorta in a forested setting in the introduced range. P. contorta invasion explained more of the decline in species richness in the introduced than native range. Native species composition changed more strongly across the invasion gradient in the introduced than native range. Litter depth increased more rapidly with P. contorta cover in the native than introduced range.Main conclusions Our results highlight the potential of pines to alter plant communities whether encroaching from forests in the native range or from plantations in the introduced range. Species richness and plant cover declined in both settings; however, individual species abundance and species composition were more impacted in the introduced range than in the native range. We suggest that invading trees have a greater capacity to cause ecological impacts in their introduced than in their native range, particularly where they represent a novel life-form.

From individuals to communities: How singleton invasive pine saplings lead to biodiversity change in the Brazilian Cerrado hotspot

“…As expected, the two habitats have, however, distinct species composition, crucially in the shrub layer (Figure ). This suggests that the invasion time has not been sufficient yet to lead to overall changes in species composition at this early stage of invasion, in line with other evidence (Taylor et al., ).…”

“…However, other investigations have found a positive relationship between diversity and pine invasion; for example, associated with increased pine dominance in forest‐dominated habitats (e.g. Taylor et al., ), in which more shade‐resistant species are able to establish. By showing that vegetation layers (shrub and grass in our case) can respond differentially to the presence of invasive pine trees and that this response can change as saplings grow larger, our results help resolve the paradox of the inconsistent impact of these trees on local biodiversity.…”

Severity of impacts of an introduced species corresponds with regional eco‐evolutionary experience

“…However, these sites likely had fairly stable vegetation types over long time periods. Where P. contorta has recently established into open habitats a similar decline in species richness was observed in both native and introduced ranges (Taylor et al ), supporting the idea that the eco‐evolutionary experience of the receiving community is important, even within the native range.…”

“…For example, previous studies in Patagonia found that exotic conifer plantations were associated with lower native biodiversity than native forests (Paritsis and Aizen , Fajardo and Gundale ). Naturalized stands were also found to have negative impacts on plant diversity at sites in New Zealand, Chile and Argentina (Ledgard and Paul , Dickie et al 2011, Taylor et al , Franzese et al ). In contrast, a study in Sweden showed that plant diversity in P. contorta plantations was similar to native P. sylvestris stands (Nilsson et al ).…”

Insights on the persistence of pines (Pinusspecies) in the Late Cretaceous and their increasing dominance in the Anthropocene

“…In this paper, we use the term “Anthropocene” to refer to the period during which human activity has become the dominant influence on climate and the environment. Many pine species have undergone major range expansions in the Anthropocene by expanding their ranges in the Northern Hemisphere (Améztegui, Brotons, & Coll, ; Jakubos & Romme, ; Lubetkin, Westerling, & Kueppers, ; Prévosto, Hill, & Coquillard, ; Taylor, Maxwell, Pauchard, Nuñez, & Rew, 2016b; Taylor et al., 2016a) and, due to large‐scale plantings and invasions, mainly in the Southern Hemisphere (Essl, Mang, Dullinger, Moser, & Hulme, ; Richardson, Williams, & Hobbs, ; Simberloff et al., ). Pine is the dominant taxon in natural forests over parts of the Northern Hemisphere (Richardson, ), and more than 20% of pine species are invasive in regions outside their native ranges (Nuñez et al., ; Rejmánek & Richardson, ; Richardson & Rejmánek, ; Rundel, Dickie, & Richardson, ; Simberloff et al., ).…”