Safeguard and Protection of Mediterranean Sea Daffodil (Pancratium Maritimum L.): A Case of Extinction in Progress?
Project location: ITALY, Naples, Palermo, Mediterranean Coast
Project start date: November 2012 - Project end date: November 2015
Project number: 2012-083
Beneficiary: Dipartimento di Biologia, Università degli Studi di Napoli Federico II
Timeline for this final report: From November 2012 to March 2016
The Mediterranean basin is one of the most biodiverse temperate regions of the world. Such richness is a consequence of several causes, e.g., geographic position, complex geological history, and prolonged coexistence with human activities. All of these causes have contributed to the simultaneous presence of various bioclimatic areas and environments, along with the occurrence of species whose geographic distributions reflect different past events. In addition, the Mediterranean Sea and its coastlines have also experienced dramatic changes in configuration due to climate change over the last ten million years, which determined extreme changes in marine levels. In this complex framework, sea daffodil (Pancratium maritimum L., Amaryllidaceae) has experienced more or less all of these vicissitudes and it is an interesting plant to study both as possible model species and especially for its preservation. It is important to highlight that a fundamental prerequisite for planning a conservation strategy for all species is having a thorough “knowledge” of them, i.e.: understating its ecology, biology (life cycle), and genetics. Generally, as an example, up to date species genetic information are not always comprehensively investigated, often causing wrong conservation managements. In fact, it is impossible to perform a correct conservation programme about an organism if its genetic diversity is not investigated.
Briefly, sea daffodil is a perennial bulbous plant with beautiful white flowers and it is an important component of all Mediterranean coastal dune vegetation. It is a plant very appreciate for its beauty and pharmacological proprieties since early times (e.g., Aegean Bronze Age civilization, ∼3500 BC). This plant is currently endangered along the Mediterranean coasts due to the loss of its natural habitat caused by human pressure (i.e., sunbathing, excess flower sampling, and sand dune erosion). Nevertheless, this species is not yet not evaluated by the IUCN (International Union for Conservation of Nature, Red List, http://www.iucnredlist.org/apps/redlist/search). A notable example of the severity of the endangered status of the species is its total disappearance from the island of Ischia (Naples, southern Italy) due to human impact.
This project received a grant from the Nando and Elsa Peretti Foundation in order to perform a multi-disciplinary study about the sea daffodil to have an informative database that could provide the scientific community sufficient information to plan a correct strategy for its conservation (i.e., preservation and protection). The project has been performed through three different research approaches: (1) genetics, (2) Geographic Information System (GIS) and (3) eco-morphology.
The results achieved through genetic data, GIS and morpho-ecological investigations will be then used to apply Species Distribution Models (SDMs) to evaluate several aspects of sea daffodil biology, e.g.: to estimate its range in the past, present and near-future; to discover which climatic variables (past, present and near-future) are correlated with the genetic “health” of sea daffodil; and to assess if the modern human pressure is really deleterious to its survival.
Over a three years’ time, the aforementioned different methodological approaches have been completed, producing a degree thesis in Natural History, a PhD thesis in Advanced Biology, articles published and submitted for publication in peer-reviewed international journals, and two Italian Botanical Society (SBI) interim report books.
Description of the three activities implemented are reported below for each research approach.
(1) Molecular approach: analyses of genetic diversity.
This was the main priority objective of the project, as already introduced above. A total of 867 mature individuals were sampled from 48 localities (=populations), covering most of the distribution area of the sea daffodil and representing as much diversity in ecological conditions as possible. Through the analyses of the DNA (chloroplast and nuclear DNA) of each individual, it clearly resulted that the analysed populations showed a high genetic diversity and no inbreeding was detected. These data are very important because the species keeps a good “health status” and it has all prerequisite to avoid inbreeding depression or negative effects caused by low genetic diversity. In addition, analysing the genetic patterns obtained, it has been observed that sea currents have great importance in the distribution of the species, also confirmed by the particular morphology of its seeds (possible floating ability).
(2) GIS approach: analyses of its geographical distribution (past, present and near-future period) and impact of climatic and human variables on its genetic diversity.
The 48 sea daffodil populations used in the previous genetic analyses (1) were geo-referenced using the GIS and overlapped on the ortho-photo of Google Earth.
To infer how the present human impact affects the 48 sea daffodil populations sampled, the Global Human Footprint Database was used (http://sedac.ciesin.columbia.edu/). Briefly, for each population was calculated an index of human pressure (Human Footprint Value, HFP) which considers the human population density, human land use and infrastructure (built-up areas, night-time lights, and land use/land cover), human access (coastlines, roads, railroads, and navigable rivers) for each sea daffodil locality analysed.
According to our analyses, the level of human pressure in the sampled sea daffodil populations was moderately high even if there is no correlation with the genetic diversity of each population obtained in the point (1). This could indicate that the present human pressure has not “yet” affected the genetic diversity of this bulbous plant.
A similar correlation analysis was also used considering the climatic variables for each sampled locality thanks to World Climate Database (http://www.worldclim.org/) and the corresponding genetic data obtained in this project (1). A significant positive correlation was observed between the genetic distance and precipitation of the coldest quarter variable, which suggests the importance of rainfall for the fitness of the plant (i.e., flowers production).
Finally, to evaluate current, past [last glacial maximum, LGM (∼21.000 years ago) and last interglacial (∼120-140.000 years ago)] and near-future (2070) presence suitability for sea daffodil, we trained Species Distribution Models (SDMs). Five hundred and thirty-seven occurrence data were used for the training of SDMs, gathered from our database literature, public databases and personal communication with experts. Also in this case, the total 537 localities were geo-referenced using GIS and overlapped on the ortho-photo of Google Earth (as above introduced). The current potential distribution of sea daffodil was predicted to occupy the coastline of the entire Mediterranean basin, also including the southern and north-western coasts of the Black Sea. In addition, suitable areas were predicted along the eastern coast of the Atlantic Ocean, ranging from northern Africa to France. When projected over past environments, species potential distribution resulted less extended than the current one, especially the predictions for LGM. When projected to 2070 (near-future), the sea daffodil potential distribution was predicted to widen its extent in its southern and northern margins.
(3) Eco-morphological approach: analyses on micro-morphology structures to understand the adaptations employed nearby sand dune habitat.
The present study aimed to know the sea daffodil adaptations compared with its habitat. In fact, it is well known that sandy coasts are affected by selective environmental pressures, such as salt spray, low levels of nutrients and freshwater availability, strong sun radiation, unstable soil and sand-blasting. These stress conditions closely interact as abiotic modulators of leaf adaptation, since specific patterns in leaf morphology directly govern the physiological performance and the associated plant environment relationships, which are important to ensure plant survival, especially in stressful habitats.
For this scope, it has been analysed the morphological variation in leaf traits among different eleven populations of sea daffodil and four similar Pancratium species of different habitats (P. foetidum, P. Illyricum, P. linosae, P. sickenbergeri) as well as to correlate the leaf diversity with climate conditions present in the different sampled localities.
The populations of sea daffodil were chosen from a range of sites of the central-eastern Mediterranean coastal sand dunes. According to the results obtained, sea daffodil presents a leaf structure rather uniform, but many significant differences were detected among the studied populations and with the other species. The observed population variation in leaf traits reflects an important phenotypic plasticity among populations of sea daffodil associated with different local climatic regimes that may facilitate plant survival under stressed environmental conditions of sand dunes. Summarizing, the results of this study showed that there are significant levels of leaf morphometric variation across sea daffodil populations, which are consistently correlated to general climate parameters (mean temperature and precipitation), indicating that the modifications of leaf architecture are important anatomical and physiological strategies to help the sea daffodil reducing water loss through leaves and increasing water use efficiency.
Thanks to these studies, we have also focused about the structure of sea daffodil’s roots and their importance permitting the survival of the plant in its stressed environment. In fact, through some analyses, we have observed the presence of fungal colonization also into the roots of the sea daffodil populations. Successively, using a molecular approach trough the DNA barcoding (sequencing of markers species-specific), the fungi has been characterized as arbuscular mycorrhizal fungi (AMF). It is common knowledge among botanists, that these fungi are very important for the plants because permit the survival in hard conditions as for example in the sand dunes habitat. So, it is important to consider this mutualist association in the conservation procedure for this plant because the presence of this fungi are fundamental for the life cycle of the sea daffodil.
Thanks to this grant obtained by the Nando and Elsa Peretti Foundation, a complete study has been performed about sea daffodil (Pancratium maritimum), revealing important information to plan concrete strategies for its conservation. Summarising, the sea daffodil showed to be a plant well adapted to the difficult conditions of sand dunes, where it uses different reproductive strategies depending on the environmental and human pressures (e.g., presence of a bulb, vegetative reproduction, out/in-crossing pollinations, floating seeds, presence of AMF in the roots). In addition, the presence of a bulb permits to the plant to survive under difficult climatic conditions and to the indiscriminate flower harvest. It is important to note that all of the analysed populations present strong human pressure, which today can point to the genetics of this species when the plant was “totally” eradicated, determining an evident bottleneck with loss of genetic diversity and all negative consequence of this (inbreeding depression, genetic drift and so on). To date, the genetics of plant is healthy and its range is expanding, peaking in the next future, supposing good capacities of resistance, adaptability, and resilience as observed both by genetics and eco-morphological analyses (point 1, 3).
(A) Rapporti evolutivi nel genere Pancratium L. nel bacino del Mediterraneo. [Evolutive relationships in the genus Pancratium L. in the Mediterranean bacin]. PhD thesis in Advanced Biology, XXV cycle, Dr. Antonietta Di Maio.
(B) Analisi molecolari e studio filogeografico in Pancratium maritimum L. (Amaryllidaceae). [Molecular analyses and phylogeography of Pancratium maritimum L. (Amaryllidaceae)]. Degree thesis in Natural History (2012-2013), Dr. Sara Barbarito.
(C) Development and characterization of 21microsatellite markers for Pancratium maritimum L. (Amaryllidaceae). 2013. Antonietta Di Maio, Olga De Castro. Conservation Genetics Resources 5: 911-914.
(D) What do leaf anatomy and micro-morphology tell us about the psammophilous Pancratium maritimum L. (Amaryllidaceae) in response to sand dune conditions? Rosaria Perrone, Cristina Salmeri, Salvatore Brullo, Paolo Colombo, Olga De Castro. 2015. Flora 213: 20-31.
(E) Aggiornamenti e novità sulle conoscenze di Pancratium maritimum (Amaryllidaceae). Olga De Castro, Antonietta Di Maio, Gennaro Imparato, Errol Véla, Sara Barbarito, Giancarlo Sibilio, Bruno Menale, Simona Carfagna, Giovanna Salbitani, Claudia Di Martino, Giuseppe Palumbo, Claudia Bottone, Marco Guida, Paolo Colombo, Salvatore Brullo, Cristina Salmeri, Rosaria Perrone. 2014. In: Floristica, Sistematica ed Evoluzione. Società Botanica Italiana, Firenze. Pp. 39-40.
(F) Comparative leaf micromorphology, anatomy and architecture in some Mediterranean species of Pancratium (Amaryllidaceae). Cristina Salmeri, Rosaria Perrone, Paolo Colombo, Salvatore Brullo, Olga De Castro. 2015. In: Approfondimenti floristici e sistematici sulla flora d’Italia. Società Botanica Italiana, Firenze. Pp. 55-56.
Articles submitted and in preparation:
(G) An evolutive snapshot of the Mediterranean sea daffodil (Pancratium maritimum L.): comparing past, present and future. Olga De Castro, Antonietta Antonietta Di Maio, Mirko Di Febbraro, Gennaro Imparato, Michele Innangi, Errol Véla, Bruno Menale. 2016. Annals of Botany, submitted.
(H) Molecular characterization of arbuscular mycorrhizal fungi in sea daffodil (Pancratium maritimum L.). Olga De Castro, Bruno Menale. Plant Biology, submitted.
(I) Detection of maternal chloroplast inheritance in controlled crosses in the sea daffodil Pancratium maritimum L. (Amaryllidaceae). Olga De Castro. In preparation.
(L) Origins and evolution of sea daffodil (Pancratium maritimum L., Amaryllidaceae): a phylogenetic and historical biogeographical analysis. Olga De Castro, Errol Véla, Bruno Menale. 2016. In preparation.