UNCORRECTED PAGE PROOFS • © 2010 Sinauer Associates, Inc. This material cannot be copied, reproduced, manufactured, or disseminated in any form without UNIT FOUR express written permission from the publisher. Evolutionary History of Lineages and Biotas UNCORRECTED PAGE PROOFS • © 2010 Sinauer Associates, Inc. This material cannot be copied, reproduced, manufactured, or disseminated in any form without express written permission from the publisher. Previous Page: The Hawaiian Islands. Courtesy of Jeff Schmaltz, MODIS Rapid Response Team, NASA/GSFC. 10 Th e Ge o g r a p h y o f Diversification In Unit 3, we learned that the evolutionary fates and distributions of The Fundamental Geographic species have been dynamic throughout the history of life on Earth. Patterns 362 New species have continuously evolved from ancestral species, Endemism and Cosmopolitanism 365 and occasionally, large numbers of species have been eliminated in The origins of endemics 368 an episode of mass extinction followed by the evolution of entirely Provincialism 370 new sorts of species. Species distributions often have changed, either through jump dispersal of founding individuals or populations across Terrestrial regions and provinces 370 a barrier, or through more gradual range expansion over continuous Marine regions and provinces 384 expanses of suitable habitats. Some of the most profound changes in Classifying islands 388 distributions have come when entire groups of species have crossed Quantifying similarity among biotas 392 from one biogeographic region to another following the erosion of Disjunction 396 a barrier. Additionally, we learned that the geology of the Earth it- Patterns 396 self changes continuously through time and that at various times and Processes 398 particularly over the past several million years, climatic cycles have Maintenance of Distinct Biotas 399 produced an exceedingly dynamic ecological arena. In order to avoid Barriers between biogeographic regions 400 extinction, species and biotas have had to respond to frequent and Resistance to invasion 400 unpredictable changes in habitat structure and distribution through dispersal or adaptation. In short, while evolutionary diversification Avian migration and provincialism 401 occurs over time, it also has a distinct spatial dimension, and as a way Biotic Interchange 404 of thinking about the contributions of both, we recognize here two The Great American Biotic Interchange 406 kinds of “histories” that have shaped the characteristics of contem- The Lessepsian exchange: The Suez Canal 412 porary biotas, which we will call the history of place and the history of The Divergence and Convergence of lineage (Brown 1995). Isolated Biotas 413 The history of place is the history of the Earth itself: the changes in Divergence 413 geography, geology, climate, and other environmental characteristics Convergence 415 that are extrinsic to the particular organism, lineage, or biota being studied. We like to think of the history of place as the environmen- Overview 421 tal and geographic template that each organism, lineage, or biota has experienced during its own unique evolutionary history. Thus, the history of place includes the geological and climatic history of the Earth; changes in soils, climate, and oceanographic and limnological conditions; and the varying composition of biotic communities. Past environments may have influenced a contemporary lineage in many UNCORRECTED PAGE PROOFS • © 2010 Sinauer Associates, Inc. This material cannot be copied, reproduced, manufactured, or disseminated in any form without express written permission from the publisher. 362 ChAPTeR 10 ways by influencing the abundance, distribution, and adaptive evolutionary changes of its ancestors. Even the most distantly related kinds of organisms that lived together in the past at a particular place—and hence, experienced some features of a common environment—share some history of place. The history of lineage is the series of changes that have occurred in the in- trinsic characteristics of organisms, species, or higher taxa over generations of evolutionary descent. These are changes in heritable characteristics, derived from and constrained by the characteristics of the organisms’ ancestors. Only to the extent that organisms share common ancestors do they share a history of lineage. The history of place strongly influences the history of lineage, be- cause characteristics of past environments (e.g., geology, climate, and biotic composition) undoubtedly influenced the survival, distribution, and diversi- fication of all lineages that occurred in those places. But the converse is less true. The history of lineage influences the history of place only to the extent that the activities of particular organisms altered the past environment for themselves and other lineages. While many kinds of organisms substantially modify their environments—the building of reefs and atolls by corals, and the modification of the climate of the Amazon basin by rain forest trees are just two examples—usually these influences are diffuse and cannot be attrib- uted to just one lineage or taxonomic group. In this chapter, we describe the fundamental biogeographic patterns that emerge from a history of diversification, dispersal, and extinction of lineages and biotas on a geologically and climatically dynamic Earth. We first con- sider general patterns of endemism, provincialism, and disjunction and the abiotic and biotic features that function to maintain geographically separate biotas. We then consider what happens when barriers between previously separate biotas erode, opening corridors for biotic interchange. We finish this chapter with a discussion of several general evolutionary trends that tend to arise when lineages and biotas have long been separated by geographic bar- riers. In Chapter 11, we present an overview of approaches to reconstructing the history of lineages, and then in Chapter 12 we build on that discussion by introducing the variety of approaches available for reconstructing historical relationships between lineages, biotas, and places. The Fundamental Geographic Patterns The most pervasive feature of geographic distributions is the fact that they have limits. No species is completely cosmopolitan (organisms that are wide- ly distributed throughout the world), and most species and genera, and even many families and orders, are confined to restricted regions, such as a single continent or ocean—the term endemic means occurring in one geographic place and nowhere else, and it can be applied at any taxonomic scale. Many distributions are extremely limited. The minute, redfinned blue-eye (Sca- turiginichthys vermeilipinnis), the sole species in the fish genus Scaturiginich- thys, lives in a handful of tiny springs in arid western Queensland, Australia (Ivantsoff et al. 1991), which it shares with another equally restricted species, the Edgbaston goby (Chlamydogobius squamigenus; Larson 1995; Figure 10.1). On the other hand, even very depauparate taxa can also have broad distribu- tions. The avian family Opisthocomidae contains only a single species, the bizarre hoatzin (Opisthocomus hoazin)—a nearly flightless, leaf-eating bird— but in contrast to the redfinned blue-eye, the hoatzin occurs across a fairly large expanse of the Amazon and Orinoco river drainages of northern South America (see Figure 10.1). More diverse taxa tend to be endemic within larger areas. For example, the avian family Furnariidae (ovenbirds), with more than 65 genera and 300 species, is endemic to South and Central America plus sev- UNCORRECTED PAGE PROOFS • © 2010 Sinauer Associates, Inc. This material cannot be copied, reproduced, manufactured, or disseminated in any form without express written permission from the publisher. 363 S. vermeilipinnis O. hoazin F. rufus Figure 10.1 Endemism occurs across eral neighboring islands (one species extends north to northern Mexico; see a broad range of geographic scales and Figure 10.1). Several large fish families, including catfish eels (Plotosidae), is often decoupled from taxonomic di- are confined to the Indo-Pacific region. In South and Central America, there versity or phylogenetic distinctness. The are over 50 families and subfamilies of flowering plants that occur nowhere hoatzin (Opisthocomus hoazin) represents else; many of these are small taxa, but they also include several extremely a highly unique species and genus of bird in the Amazon and Orinoco river basins diverse families. Cacti (Cactaceae) and bromeliads (Bromeliaceae) would be of northern South America (green area). endemic to the New World if one species of each had not recently crossed the The ovenbirds (Furnariidae: the Rufous ocean by natural means (long-distance dispersal) and become established in hornero, Furnarius rufus, shown here) Africa. However, there are notable exceptions, with even some diverse taxa represent a diverse Neotropical family of Sinauer Associates, Inc. having very restricted distributions. We have already discussed, for example, suboscines with over 65 genera and 300 LOMOLINO species (yellow dashed area). The African the extreme diversity of cichlid fishes in the Great BiogeographyLakes of the African Rift cichlids represent a complex of over 1400 Valley (Chapter 7; see Figure 10.1). Fig. 10.01 03.30.10 very closely related species in 12 African Endemics are not distributed randomly, but tend to overlap with other lakes (blue area) (see Chapter 7) The geographically restricted species in certain regions,