Alessandro Chiarucci

Anthropogenic drivers of plant diversity: perspective on land use change in a dynamic cultural landscape

Changes in land use are among the forces shaping Earth’s surface. In many industrialized areas, the loss of a traditional state of dynamic equilibrium between traditional management and natural dynamics is followed by abandonment to regeneration processes. This can reduce ecological complexity at the landscape scale and negatively affect biodiversity patterns. In this study, we investigate the relation between land use change and plant species diversity in the network of protected areas (PAs) of the province of Siena (Tuscany, Central Italy). This is an area characterized by long-lasting human activities and highly renowned cultural landscapes. We used remotely sensed, mapping and ground based plant compositional data, to investigate the present pattern of plant species diversity, the changes of landscape structure and changes in forest habitats. Most of the plant diversity present in this network of PAs is due to broad scale gradients due to ecological diversity but also to human management. Most of the area is currently covered by forests and analysis of a historical sequence of spatial data reveals that this is largely a consequence of the abandonment of traditional management during the last decades. Finally, focusing on forest succession as a consequence of land use change, we demonstrate that species richness significantly declines with increasing age of forest stands. Taken together, our results confirm that the recent trends of rural abandonment are leading to homogenization and biodiversity loss in traditional landscapes of Mediterranean Europe. We discuss implications for policy, and suggest that PA management in cultural and historical landscapes should pay increasing attention traditional anthropic practices.

Natural and human impact in Mediterranean landscapes: An intriguing puzzle or only a question of time?

Abstract Time is a key factor to understand the effects of disturbance on natural communities or ecosystems. In Mediterranean landscapes, where nature and humans have been strongly intermingling since mid-Holocene, the relationships between plant ecology and palaeoecology and their role for the interpretation of natural and anthropogenic changes still needs to be clearly understood. Ecology and palaeoecology are both investigating such problems, but each of them cannot disentangle the specific role played by nature and by humans in shaping the present plant communities and landscapes. A new age of cooperation among researchers in ecology and palaeoecology is needed, and the integration of these closely related but separated research fields is necessary to explain the resulting dynamic puzzle. Plant ecologists should avoid the oversimplification of the actual causes as the exclusive drivers of plant communities and landscapes and force the exploitation of the available data to generate and test new hypotheses for past, present and future environmental reconstructions and management. Even when planning for the future biodiversity conservation, we need to properly use the existing information about millennia of human effects on the natural biotas, to properly set landscape management and conservation priorities.

Anticipating species distributions: Handling sampling effort bias under a Bayesian framework

Anticipating species distributions in space and time is necessary for effective biodiversity conservation and for prioritising management interventions. This is especially true when considering invasive species. In such a case, anticipating their spread is important to effectively plan management actions. However, considering uncertainty in the output of species distribution models is critical for correctly interpreting results and avoiding inappropriate decision-making. In particular, when dealing with species inventories, the bias resulting from sampling effort may lead to an over- or under-estimation of the local density of occurrences of a species. In this paper we propose an innovative method to i) map sampling effort bias using cartogram models and ii) explicitly consider such uncertainty in the modeling procedure under a Bayesian framework, which allows the integration of multilevel input data with prior information to improve the anticipation species distributions.

Plant recording across two centuries reveals dramatic changes in species diversity of a Mediterranean archipelago

Although islands are model systems for investigating assembly of biological communities, long-term changes in archipelago communities are not well understood because of the lack of reliable data. By using a vast amount of floristic data we assembled a dataset of the plant species occurring on 16 islands of the Tuscan Archipelago, Italy, across two periods, 1830–1950 and 1951–2015. We collected 10,892 occurrence records for 1,831 species. We found major changes in the island plant assemblages between the two periods, with native flora significantly decreasing (−10.7%) and alien flora doubling (+132.1%) in richness. The species–area relationships demonstrated the scale-dependence of the observed changes for native and alien species. The observed floristic changes were dependent on island area, with smaller islands displaying high variability in richness and compositional changes and larger islands having more stable species assemblages. The richness of species associated with open landscapes, that had been maintained for centuries by traditional practices, markedly reduced while the number of woody species, associated with afforestation processes and invasion by alien woody plants, significantly incresed. These results demonstrate the great power of floristic studies, often available in grey literature, for understanding long-term biotic changes in insular ecosystems.

Shrines in Central Italy conserve plant diversity and large trees

Sacred natural sites (SNS) are instances of biocultural landscapes protected for spiritual motives. These sites frequently host important biological values in areas of Asia and Africa, where traditional resource management is still upheld by local communities. In contrast, the biodiversity value of SNS has hardly been quantitatively tested in Western contexts, where customs and traditions have relatively lost importance due to modernization and secularization. To assess whether SNS in Western contexts retain value for biodiversity, we studied plant species composition at 30 SNS in Central Italy and compared them with a paired set of similar but not sacred reference sites. We demonstrate that SNS are important for conserving stands of large trees and habitat heterogeneity across different land-cover types. Further, SNS harbor higher plant species richness and a more valuable plant species pool, and significantly contribute to diversity at the landscape scale. We suggest that these patterns are related not only to pre-existent features, but also to traditional management. Conservation of SNS should take into account these specificities, and their cultural as well as biological values, by supporting the continuation of traditional management practices.

The Influence of Vegetation and Landscape Structural Connectivity on Butterflies (Lepidoptera: Papilionoidea and Hesperiidae), Carabids (Coleoptera: Carabidae), Syrphids (Diptera: Syrphidae), and Sawflies (Hymenoptera: Symphyta) in Northern Italy Farmland

ABSTRACT n Landscape structure as well as local vegetation influence biodiversity in agroecosystems. A study was performed to evaluate the effect of floristic diversity, vegetation patterns, and landscape structural connectivity on butterflies (Lepidoptera: Papilionoidea and Hesperiidae), carabids (Coleoptera: Carabidae), syrphids (Diptera: Syrphidae), and sawflies (Hymenoptera: Symphyta). Vegetation analysis and insect samplings were carried out in nine sites within an intensively farmed landscape in northern Italy. Plant species richness and the percentage of tree, shrub, and herb cover were determined by means of the phytosociological method of Braun-Blanquet. Landscape structural connectivity was measured as the total length of hedgerow network (LHN) in a radius of 500 m around the center of each sampling transect. Butterflies species richness and abundance were positively associated both to herb cover and to plant species richness, but responded negatively to tree and shrub cover. Shrub cover was strictly correlated to both species richness and activity density of carabids. The species richness of syrphids was positively influenced by herb cover and plant richness, whereas their abundance was dependent on ligneous vegetation and LHN. Rarefaction analysis revealed that sawfly sampling was not robust and no relationship could be drawn with either vegetation parameters or structural connectivity. The specific responses of each insect group to the environmental factors should be considered in order to refine and optimize landscape management interventions targeting specific conservation endpoints.

Methodological issues in exploring cross-taxon congruence across vascular plants, bryophytes and lichens

The effectiveness of surrogate taxa as ecological indicators for biodiversity assessment and monitoring depends on different factors, such as the spatial scale of analysis. In this study, we explored the effects of the grain size and the choice of predictor variables on the strength of the community congruence relationships among vascular plants, bryophytes and lichens. Community data for these taxa were collected using a restricted random sampling applied in the Bosco di Sant’Agnese Nature Reserve (Tuscany, Italy). Co-correspondence analysis (Co-CA) was performed on two different response communities (e.g. bryophytes and lichens), considering three predictors (presence/absence of vascular plant, abundance of vascular plants and data on the vegetation structure in each plot) for three grain sizes (1 m2, 100 m2 and 10,000 m2). The effects of spatial grain and the type of predictor variable on the strength of the congruence among the considered taxonomic groups were twofold: (i) the amount of explained variance depends on the grain size and on the analysed taxon; it increased with increasing grain size for bryophytes while showing, in general, an opposite pattern for lichens; and (ii) the observed relationships mainly depend on the choice of predictor variables. The highest predictive power for bryophytes was shown by the vegetation structure predictor, while for lichens it was shown by the presence/absence of vascular plants. Our results highlight the importance of plot dimension, the choice of type of data used as predictors and taxon identity in evaluating cross-taxon relationships and provide further insights into the limitations of cross-taxon estimates among vascular plants and cryptogams for biodiversity assessment and conservation planning.

Are available vegetation data suitable for assessing plant diversity? A study case in the Foreste Casentinesi National Park (Italy)

This paper aimed to analyze potentials and shortcomings of existing vegetation data collected in an Italian National Park (Foreste Casentinesi NP) to: (1) assess coarse scale patterns of species diversity, and (2) set up a habitat monitoring system. We generated a specifically designed georeferenced dataset by assembling all available forest vegetation data, and then we analyzed spatial and temporal patterns of data by sample-based accumulation and rarefaction curves. The analyses were performed on data gathered from the year 1934 to 2007. This broad temporal range may provide valuable information about processes occurring over a longer period than the majority of the published resurvey studies. Our study revealed an uneven distribution of the records both in time and space, corroborating the view that this type of data is inappropriate to analyze trends of plant diversity at coarse scale. However, especially the oldest records of the dataset represent a valuable source of information about long-term plant diversity changes, if used in resurvey studies designed with proper techniques. Detecting the directions of vegetation, or habitat, dynamics is crucial for addressing effective conservation actions.

Aquatic Plant Diversity in Italy: Distribution, Drivers and Strategic Conservation Actions

Italy is recognized as one of the prominent hot spot areas for plant diversity at regional and global scale, hosting a rich range of ecosystems and habitat types. This is especially true considering aquatic habitats, which represent a major portion of the total water surfaces in the Mediterranean region. Nevertheless, only a scant attention was paid to clarify the species richness of aquatic plant and its contribution to the total diversity at the country scale, despite such plants are seriously threatened at multiple scales. This paper provided the first comprehensive inventory of aquatic plants at the whole country scale, collecting data on species’ distribution, trends, and explanatory determinants of species richness. We confirmed the key contribution of Italy to the regional and global aquatic plant diversity with a total of 279 species recorded since 2005, equal to the 88.5%, 55.9% and ∼10% of the richness estimated at European/Mediterranean, Palearctic and global scale, respectively. Ten species are considered extinct in the wild [among which Aldrovanda vesiculosa L., Caldesia parnassifolia (Bassi ex L.) Parl., Helosciadium repens (Jacq.) W.J.D. Koch, and Pilularia globulifera L.], four were doubt [among which Luronium natans (L.) Raf., Utricularia intermedia Hayne, and U. ochroleuca R.W. Hartman.], and eight were erroneously reported in the past, among which Isoëtes lacustris L., Myosotis rehsteineri Wartm., and Ranunculus aquatilis L. Only 18 species – mainly helophytes (14) – were present in all the 20 Italian regions, whereas hydrophytes showed most scanty regional frequencies. Temperature, latitude, area and water resources availability are the main drivers of aquatic plant spatial arrangement and diversity. Furthermore, the number of inhabitants per km2 well described the number of “lost species” since 2000. The findings of the present survey call for an urgent elaboration of large-scale strategies to ensure the survival of aquatic plants, stressing on multiple functions played by aquatic plants in supporting national economy and human well-being. In this context, Italy can play a fundamental role guaranteeing temporary refuge for projected or expected species migrations along latitude and longitude gradients. Besides, in hyper-exploited landscapes man-made water bodies can further enhance the achievement of minimum conservation targets.

Biogeography and ecology of the genus Turbinicarpus (Cactaceae): environmental controls of taxa richness and morphology

The biogeography and the ecology of the genus Turbinicarpus are scarcely known and the taxonomic segregation of the genus Rapicactus from Turbinicarpus has been debated. The present study aims to (i) evaluate the distribution of all taxa of Turbinicarpus in the full distributional range of the genus (NE Mexico); (ii) investigate the potential ecological divergence between Rapicactus and Turbinicarpus; and (iii) analyse the influence of environmental variables on plant morphology. The distribution pattern of all taxa belonging to the genus Turbinicarpus s.l. (Turbinicarpus + Rapicactus) was mapped using information from 12 herbaria, as well as unpublished databases. The study area was divided into cells of 25 km × 25 km. The relationships between taxa richness, sampling effort and environmental variables were tested by using grid data, via spatially explicit models. The elevational distribution of populations and the effects of climate, latitude and elevation on the mean steam diameter of the populations were separately investigated for Turbinicarpus and Rapicactus. Turbinicarpus s.l. taxa richness is highest within 100°W and 101°W longitude, about 2500 km north of the equator, with maximum diversity in areas with a mean annual temperature of 17–19 °C and a mean annual rainfall of 550–650 mm. A significant relationship was observed between taxa richness and sampling effort, and between taxa richness and longitude, mean annual rainfall and calcium-rich substrate. Rapicactus taxa were found to grow at higher elevations compared with Turbinicarpus. Body size of the plants showed a negative relationship with latitude and elevation in Turbinicarpus, and a positive one with latitude in Rapicactus. The results showed that the genus Turbinicarpus s.l. presents diversity hotspots in the floristic regions of Chihuahuan Desert and Sierra Madre Oriental. The responses of Rapicactus and Turbinicarpus to latitudinal and elevational gradients were different, supporting the segregation of Rapicactus from Turbinicarpus.