A Mediterranean history

The Mediterranean region has had a long and complex history. The phasing of three main historical elements forms a Mediterranean triptych: geology, climate, and human activities. The geological fragmentation of the Mediterranean into distinct microregions and tectonic movement of its different microplates has continually reshaped the configuration of the terrestrial landscapes, islands, and mountains. Many areas have been land bridge connections across the sea. The Mediterranean region has a characteristic climate, the essential element of which is the occurrence of a summer drought. Although initial trends towards aridity are ancient, the Mediterranean climate only dates to the Pliocene. Climatic oscillations since its onset have caused sea level changes, influencing the appearance and disappearance of land bridge connections across different parts of the Mediterranean Sea, causing species’ range sizes to expand and contract in repeated phases. Finally, nowhere else in Europe has had such a long history of human presence and activity. In the last three millennia, the impact of human activities on the landscape has been dramatic in terms of the evolution of the mosaic landscape we now observe. The phased history of these three factors is at the heart of plant evolution in the Mediterranean.

Plant reproduction

Population history and colonization dynamics in the Mediterranean mosaic landscape have closely interacted with natural selection to shape patterns of variation in mating systems and the evolution of floral traits and polymorphisms. Floral phenology is closely adapted to avoid the summer drought regime in many plant communities. Many plant species have generalist pollination systems with a complex of tight and loose interactions that affect the evolution of reproductive traits. Floral traits have clearly accompanied diversification in many groups of plants. The evolution of interactions of plants with their pollinators at the landscape and biogeographic scales illustrates intriguing examples of ongoing evolution.

The evolution of a cultural heritage

The origins of the cultivation and domestication of many fruit, legume, and cereal crops can be traced to the eastern fringe of the Mediterranean region where the ‘Fertile Crescent’ blends into the western steppe zones of the Irano–Turanian floristic province. This chapter describes this early cultivation and domestication and the traces of migration of domesticated species across the Mediterranean in the hands of human populations. The evolution of Mediterranean crops, flowers, and fruit trees during the process of domestication has involved an amazing diversity of species. Their patterns of differentiation across the Mediterranean often resemble those of wild species treated in chapter 3. This chapter also discusses the important links between human populations and plants and the growing interdependencies of these links.

Science and nature in a changing Mediterranean world

The Mediterranean world is changing, perhaps faster than we realize and faster than it ever has before. As scientists, our role here is to provide information to help integrate such changes into political decision for nature conservation. This chapter is focused on issues and approaches that allow us to perform this role and bring science and nature conservation together, and promote this venture to enhanced political will to preserve the capacity for species to evolve. The historical triptych of factors that have conditioned plant evolution in the Mediterranean presented in previous chapters is replaced here by a triad of ecological interdependencies that ultimately provide a framework to develop an ecological solidarity to conserve evolutionary potential. The chapter leads to the conclusion of this book that it is in the construction of this ecological solidarity that our true responsibility as scientists can be revealed.

One of five

There are five Mediterranean type ecosystems (MTE) with a climate characterized by a summer drought in the world. Their comparative ecology and evolution, in five geographically disjunct and distinct regions, has stimulated great interest. The similarities are striking, and after a rapid illustration of similarities in form and function (treated in detail in other work) this chapter explores the similarities that concern the evolution of species diversity and endemism. It also addresses the unique situation of the Mediterranean flora and its history, described in previous chapters. Whereas the other four MTE occur adjacent to an ocean, in a spatially limited climatic island, the Mediterranean flora has evolved around a sea, where marked historical phasing of geological and climatic change has caused the evolution of some quite unique patterns. All five MTE are biodiversity hotspots and, using illustrations from the other MTE, this chapter proposes that the similarity that we should now seek lies in an approach to conservation that integrates ecological and evolutionary processes.

Conservation in the crossroads of history

The first six chapters of this book describe the range of historical and contemporary processes that underlie the wealth, diversity, and divergence of natural populations and species in the Mediterranean flora. The processes of species divergence, adaptive trait variation along ecological transitions, interactions with pollinators and dispersal agents, and ongoing hybridization are, however, barely treated in conservation policy and action. After a presentation of the traditional approach to conservation based on rare species protection and the identification and conservation management of protected areas, this chapter presents arguments for a complementary approach based on the processes of plant evolution. Its primary proposal is that preventing further loss of evolutionary potential should become a major target of contemporary conservation strategies for the Mediterranean flora.

Plant traits and ecological dynamics

This chapter examines the multiple facets of trait variation and ecological dynamics in the contemporary Mediterranean landscape. Climatic constraints and transitions are paramount here. Diverse functional traits and strategies have evolved to avoid or tolerate the summer drought and the irregularity of spring rainfall. Annual plants do their best to avoid such constraints, and the role of functional traits in the regeneration niche and life-history strategy is undeniable. Perennial plants face the challenge of surviving their first summer and from then on illustrate a demographic persistence strategy. Dispersal and establishment generate interactions among species across a mosaic landscape where transitions between positive and negative interactions characterize successional dynamics. The study of two main features of the Mediterranean flora, its response to fire, and the diversity of aromatic plants illustrate well the importance of plant traits in the ecological dynamics of populations and communities in the mosaic landscape.

The evolution of endemic plants

In this chapter the phasing of the geological and climatic history of the Mediterranean basin is used to provide a structure for the presentation of the processes of plant diversification and in particular the evolution of endemism. In many groups of plants, evolution has occurred repeatedly during the different major phases of the region’s history. This chapter illustrates these processes and describes the major patterns of east to west diversification across the region that evolved at different times and produced the patterns described in the previous chapter. The divergence of endemic species in the different parts of the Mediterranean is the central theme. The evolution of endemism is treated at different biological levels: disjunct endemic species, geographic subspecies, and isolated populations.

The ecology and biogeography of endemism

Endemism is a primary characteristic of the Mediterranean flora. The Mediterranean region contains several zones rich in endemic species. These hotspots of endemism also have a high diversity of total species. The recurrent conjunction of endemism and high species diversity in different parts of the region represents the cornerstone of Mediterranean plant biodiversity. The causes and origins of patterns of diversity and endemism, on both a biogeographic and local scale, are the main subjects of this chapter, which will first invoke the diverse origins of the flora, a premier cause of the patterns we now observe. A major theme this chapter will then develop is the examination of correlated patterns of diversity and endemism in relation to the historical biogeography of islands and mountains that are rich in endemic plants. As the chapter advances it will become more and more apparent that the history of mountain formation is a key element in the high rates of endemic plants both in continental areas and on islands. Finally, the ecological and biological correlates of endemism are treated, in particular the niche in which endemic plants have evolved and persisted.