The genetic variation across a species’ range is an important factor in speciation and conservation, yet searching for general patterns and underlying causes remains challenging. While the majority ...of comparisons between central and marginal populations have revealed a general central–marginal (C–M) decline in genetic diversity, others show no clear pattern. Similarly, most latitudinal studies (although much fewer, especially those conducted rangewide) also showed latitudinal trends in genetic variation. To date, the C–M and latitudinal patterns have often been examined independently and have rarely been considered together when accounting for the observed genetic variation across species ranges. Here, in the light of the most recent findings, I show how latitude might be responsible for some of the deviations from the general C–M trends in genetic diversity, and vice versa. In the future, integrating latitude and range geometry with climate‐induced species migration would offer important insights into conservation prioritization across species ranges.
In their seminal paper, Shea and Chesson (Trends in Ecology & Evolution, 2002, 17, 170) developed a highly cited model (S&C model) showing scale dependency in the native–exotic richness ...relationships. Two decades later, extensive additional data have been accumulated, leading to new findings and insights. Accordingly, two updates were made here to the original S&C model: (1) changing the “negative” richness relationship between natives and exotics to “non‐consistent” or “non‐significant”; and (2) modifying the original diagram to correctly represent native and exotic species richness and their correlations across both small and large scales.
I revised the original S&C model based on two updates: (1) changing the “negative” richness relationship between natives and exotics to “no consistent” or “non‐significant”; and (2) modifying the original diagram that could correctly represent native and exotic species richness and their correlations across both small and large scales.
AIM: Little is known about the performance of plantations relative to natural forests of the same climate zone and age. China has more plantations than any other country as a consequence of massive ...afforestation efforts. We use data from China to comparatively examine tree biomass and productivity of planted and natural stands in relation to climate zone, latitude, elevation, age and species diversity (richness). LOCATION: Six forest climate/vegetation zones in China. METHODS: We used a database completed in 2007 and then updated in 2013 that contained extensive records of forest stands (10 m × 10 m plots) across China. The database records included a total of 6153 forest stands (1716 planted forests aged 0–80 years and 4437 natural forests of aged 0–400 years), located from 18.1 to 53.2° N and 75.53 to 131.8° E, and between elevations of 7 and 4240 m above sea level. These forests were grouped into six climate zones for comparisons. RESULTS: Under generally similar physical conditions (climate zones) to those in natural forests and despite having low diversity (i.e. often a single tree species), plantations aged 0–80 years already had similar biomass but much higher productivity, and thus much higher carbon sequestration rates, than natural forests. Tree biomass, productivity and their above/below ground ratios showed stronger latitudinal and elevational trends in natural forests than in planted forests. No difference in productivity was observed between the planted forests with one or two species; in natural forests, however, high diversity usually led to high productivity. MAIN CONCLUSIONS: The differences in performance between planted and natural forests were mainly explained by: (1) age (the plantations were in early succession), (2) elevation (plantations were located at lower elevations), and (3) species selection (only highly productive species were planted). As the plantations were all still young, closer monitoring of their performance is needed.
Around the globe, human behavior and ecosystem health have been extensively and sometimes severely affected by the unprecedented COVID-19 pandemic. Most efforts to study these complex and ...heterogenous effects to date have focused on public health and economics. Some studies have evaluated the pandemic’s influences on the environment, but often on a single aspect such as air or water pollution. The related research opportunities are relatively rare, and the approaches are unique in multiple aspects and mostly
retrospective
. Here, we focus on the diverse research opportunities in disease ecology and ecosystem sustainability related to the (intermittent) lockdowns that drastically reduced human activities. We discuss several key knowledge gaps and questions to address amid the ongoing pandemic. In principle, the common knowledge accumulated from invasion biology could also be effectively applied to COVID-19, and the findings could offer much-needed information for future pandemic prevention and management.
AIM: Anderson & Stebbins (1954, Evolution, 8, 378–388) posited that human activities promote species hybridizations by creating opportunities for hybridization and new habitats for hybrids to persist ...through disturbances (i.e. the ‘disturbance hypothesis’). While the first part of this hypothesis appears to be well supported, the second part has not been corroborated with empirical evidence, probably because of the lack of appropriate data. In this study, I (1) document the richness and distribution of hybrid plants in the United States; (2) examine the relationships between hybrids of different origins and between hybrid plants and native or exotic plants; and (3) examine possible mechanisms for these relationships and test the disturbance hypothesis. LOCATION: The United States. METHODS: The richness and distribution of plant hybrids was examined at the county level according to origin, that is, formed between native–native species (N × N), native–exotic species (N × E) and exotic–exotic species (E × E), using data from the Biota of North America Program. RESULTS: The three hybrid types (N × N, N × E and E × E) were positively related to each other and showed stronger positive relationship with exotic richness than with native richness. They also exhibited similar spatial patterns, with richness hotspots concentrated in the north‐east United States and Great Lakes region. However, the richness of hybrids of exotic origin (E × E and N × E) was not related to county area, as often observed for native species; instead, it showed strong positive relationships with human population density. Thus, the overall patterns of hybrid richness and distribution support the ‘disturbance hypothesis’. MAIN CONCLUSIONS: The results are generally consistent with the disturbance hypothesis. The relationship between the number of hybrids of exotic origin and overall exotic richness provided stronger evidence for human‐induced than for naturally caused hybridization, although other possible explanations may also exist.
Human activities and global change have resulted in more severe and destructive megafires in forest ecosystems worldwide. Here, I introduce and discuss the concept of “management mosaics” and how to ...use it over both space and time to mitigate the growing impacts of extreme wildfires.
Numerous islands worldwide are being increasingly invaded by exotic species. However, the effects of invading species on native floras remain underexplored, particularly whether island biogeography ...theory is applicable to native, exotic, and the newly assembled floras. Inter-group comparisons across different regions or island groups through a collection of individual studies have the potential of offering additional insights. Here, I comparatively analyze 10 datasets involving bird and plant invasions on nine island groups around the world and make detailed comparisons between two sets. I show that, although similarities exist, different taxonomic groups and different geographic settings exhibit drastically different invasion patterns on islands. Island biogeography theory still better explains native and overall (natives plus exotics) diversity patterns, such as the species-area-isolation relationships. In contrast, the corresponding patterns for exotic species are highly variable. The varying degrees of human intervention in species invasion relative to natural dispersal on different islands, along with differences between taxonomic groups, highlight the challenges of searching general patterns and applying island biogeography theories to island invasion and conservation.
The wind tunnel experiment is conducted on a simplified aircraft model with rigid and two kinds of elastic wings to investigate the effect of wing 3-D deformation on the aircraft aerodynamic ...performance. The results show that two elastic wings exhibit different aerodynamic performances, which are classified as the lift-enhancement wing and the drag-reduction wing. For the lift-enhancement wing, the stall angle is delayed from 8° to 15° with a corresponding lift increment of 64.3% compared with the rigid wing. It is shown that the lift enhancement of the aircraft model is accompanied by the torsional vibration mode of the wing, which results in the significant improvement of wing circulation. For the drag-reduction wing, the aerodynamic performance is dominated by the time-averaged deformation, which couples the bending and twisting. The wing twist reduces the effective angle of attack, as well as the frontal area, and contributes to the decreased wake deficit. Meantime, the bent wings function as barriers to the cross flow resulting in a reduction of lift-induced drag. As a result, the drag coefficient is reduced from 0.115 to 0.098 with a reduction of 14.8% at angle of attack of 12°.
•Longleaf pine was different from masting species and there was no general trend of increasing coefficient of variation (CV) in cone production through time.•On a decade scale, there was a ...significantly positive correlation between the CV of cone production and CV of average annual air temperature, but the CV of annual precipitation was negatively correlated with the CV of cone production at the Escambia (AL) and Blackwater (FL) sites.•Phase coupling of cone production with a strength of approximately 0.4 existed only between the Escambia and Blackwater sites and no significant phase coupling was found between other sites.
Longleaf pine (Pinus palustris Mill.) forests are historically and ecologically important and also endangered ecosystems in the southeastern United States. In addition to extensive exploitation and land use conversion, one characteristic which contributed to their dramatic decline and presents a continuing challenge to their future recovery is the sporadic timing of their seed production. In this study, about 60 years of cone production data for longleaf pine forests at four different sites were quantitatively characterized from different perspectives. Results indicated that longleaf pine was different from masting species and there was no general trend of increasing coefficient of variation (CV) in cone production through time. On a decade scale, there was a significantly positive correlation between the CV of cone production and CV of average annual air temperature, but the CV of annual precipitation was negatively correlated with the CV of cone production at the Escambia (AL) and Blackwater (FL) sites. Phase coupling of cone production with a strength of approximately 0.4 existed only between the Escambia and Blackwater sites and no significant phase coupling was found between other sites. The implications of these results for forest management are discussed from a perspective of spatial and temporal complexity.
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