1. 17 Biodiversity and Conservation of the Ocean Notes for Marine Biology: Function, Biodiversity, Ecology By Jeffrey S. Levinton ©Jeffrey S. Levinton 2001

2. Biodiversity Number of species explained by short-term factors such as local population crashes and flushes, colonization from other sites, leading to shuffling of a fixed pool of species, whose numbers differ from place to place. Number of species also explained by longer-term processes, i.e., speciation and extinction. In this case, need to understand what causes speciation and extinction.

3. Speciation Models Allopatric - populations are separated by a barrier (e.g., Isthmus of Panamá) and diverge genetically on either side, leading to mating incompatibility Parapatric - populations are not separated but live on either end of a strong ecological gradient, leading to natural selection acting to regionally differentiate populations. Effects can be same as allopatric model. Sympatric - species arise, even though the individuals of a population are intermixed. happens when there are two coexisting habitats, leading to strong disruptive selection and, eventually 2 subpopulations that evolve specialties to be on each of the subhabitats.

4. Causes of Extinction Habitat change or destruction Disease Biological interactions Random fluctuations of population size

5. Biogeographic Factors Geographic isolation and strong environmental gradients combine to isolate groups of species from each other

6. Biogeographic Factors 2 Geographic isolation and strong environmental gradients combine to isolate groups of species from each other Present day world consists of mostly north-south trending coasts, fairly strong latitudinal temperature gradient, offshore habitat lower in nutrients

7. Biogeographic Factors 3 Geographic isolation and strong environmental gradients combine to isolate groups of species from each other Present day world consists of mostly north-south trending coasts, fairly strong latitudinal temperature gradient, offshore habitat lower in nutrients Has led to a series of coastal biogeographic provinces, whose borders are thermal and geographically isolating discontinuities

8. ARCTIC ALEUTIAN OREGONIAN CALIFORNIAN 70N 60N 50N 40N 30N 1. Pt. Barrow 2. Cape Romanzof 3. Nunivak Island 4. Hagemeister Island 5. Prince William Sound 6. Dixon Entrance 7. Vancouver Island 8. Puget Sound 9. Cape Flattery 10. Cape Mendocino 11. Monterey Bay 12. Point Conception 13. Punta Eugenia 14. Cabo San Lucas Provinces (named in red) of the Pacific coast of North America

9. Provinces 1 Provincial boundaries are often species boundaries, but a number of species may live in two provinces or more

10. Provinces 2 In many cases provincial boundaries are also species boundaries, but a number of species may live in two provinces or more Provinces are therefore statistical constructs

11. Provinces 3 In many cases provincial boundaries are also species boundaries, but a number of species may live in two provinces or more Provinces are therefore statistical constructs The barriers between provinces are often places where currents isolate water bodies on either side of the boundary

12. Provinces 4 In many cases provincial boundaries are also species boundaries, but a number of species may live in two provinces or more Provinces are therefore statistical constructs The barriers between provinces are often places where currents isolate water bodies on either side of the boundary Within a species, provincial boundaries are often places that isolate populations, resulting in genetically distinct populations on either side of the boundary

13. Horseshoe crab American oyster Seaside sparrow Diamondback terrapin Toadfish Black sea bass South Florida is a major biogeographic barrier. This diagram shows the distribution of mitochondrial DNA variants in various species across this barrier.

14. Establishment of Biogeographic Barriers 1 Many coastal provinces are maintained by barriers to dispersal, combined with temperature breaks (e.g., Point Conception, California, Cape Hatteras, Massachusetts)

15. Establishment of Biogeographic Barriers 2 Many coastal provinces are maintained by barriers to dispersal, combined with temperature breaks (e.g., Point Conception, California, Cape Hatteras, Massachusetts) Larger scale barriers originate from geological upheavals (e.g., Isthmus of Panamá, which arose ca. 3 million years ago), resulting in isolation and speciation (in Panamá, many paired species on Pacific and Caribbean sides of Isthmus)

16. Components of Diversity Within-habitat component refers to the number of species living in the same habitat type Between-habitat component refer to the number of species living in all habitat types A within-habitat study might be comparing the number of species that live in muddy bottoms on the shelf versus the abyssal bottom

17. Diversity Gradients Latitudinal Diversity Gradient - one of the most pervasive gradients. Number of species increases towards the equator Gradient tends to apply to many taxonomic levels (species, genus, etc.)

18. Species Genera Families 1,000 100 10 Latitude Number Bivalve diversity versus latitude

19. Other Diversity Differences Between-Ocean differences. Pacific biodiversity appears to be greater than Atlantic, although the specifics are complex Within-Ocean differences. From a central high of biodiversity in the SW Pacific, diversity declines with increasing latitude and less so with increasing longitude, away from the center Inshore-Estuarine habitats tend to be lower in diversity than open marine habitats Deep-sea diversity increases, relative to comparable shelf habitats, then decreases to abyssal depths

20. Explanations of Diversity Differences Short-term ecological interactions - presence of predators might enhance coexistence of more competing species, competitor might drive inferior species to a local extinction

21. Explanations of Diversity Differences 2 Short-term ecological interactions - presence of predators might enhance coexistence of more competing species, competitor might drive inferior species to a local extinction Greater speciation rate - might explain higher diversity in tropics. Center of origin theory argues that tropics are source of most new species; some of which may migrate to higher latitudes

22. Explanations of Diversity Differences 3 Short-term ecological interactions - presence of predators might enhance coexistence of more competing species, competitor might drive inferior species to a local extinction Greater speciation rate - might explain higher diversity in tropics. Center of origin theory argues that tropics are source of most new species; some of which may migrate to higher latitudes Lower extinction rate - might also explain major diversity gradients

23. Explanations of Diversity Differences 4 Short-term ecological interactions - presence of predators might enhance coexistence of more competing species, competitor might drive inferior species to a local extinction Greater speciation rate - might explain higher diversity in tropics. Center of origin theory argues that tropics are source of most new species; some of which may migrate to higher latitudes Lower extinction rate - might also explain major diversity gradients Area - Greater area might result in origin of more species, but also lower extinction rate of species living over greater geographic ranges (having higher population sizes)

24. Explanations of Diversity Differences Habitat stability - A stable habitat may reduce the rate of extinction, because species could persist at smaller population sizes Sea-level fluctuations - sea level fluctuations, such as during the Pleistocene, might have created barriers during low stands of sea level, leading to isolation and speciation. This mechanism has been suggested as increasing the number of species in the SW Pacific in coral reef areas.

25. 0 2000 4000 6000 8000 10,000 15 10 5 Number of seagrass species Km Example of evidence supporting the center of origin theory. Number 0f seagrass species with distance downcurrent from Torres Straight

26. Eutrophic Oligotrophic Number of species Area (hectares) Example of the species-area effect as shown by species in Danish ponds and lakes. Nutrient-rich (eutrophic) ponds tend to have more species than nutrient-poor (oligotrophic) water bodies.

27. Within-ocean diversity gradients. Note strong longitudinal gradient of Corals and coral reef fishes. Latitudinal variation is slight, with drop-off At high and low latitude, probably associated with sea water temperature. After Hughes, 2001, Science

28. Expansion and Extinction on a Geological Scale We have an excellent fossil record of marine invertebrates that secreted skeletons Fossil record shows expansions, or evolutionary radiations, and major mass extinctions

29. Mass extinctions 900 600 300 Number of taxonomic families 550 400 200 0 Time before present (million years) Estimate by J. Sepkoski of changes in abundance of marine life through the geological past 1900

30. Conserving Marine Biodiversity In many habitats the number of species present is poorly known and severely underestimated Need methods of recognizing species. Morphology has limited use, but molecular markers are being used commonly to distinguish among species

31. Conserving Marine Biodiversity 2 Value of biodiversity Aesthetic value of diverse ecosystems Many species play crucial roles in elemental cycling Loss of species at apex of food chains has drastic top-down effects on marine systems Loss of species that are structural elements in communities (e.g., corals, seaweeds, seagrasses) might cause loss of many more species

32. Marine Invasions Invasion is the arrival of a species to an area that has not lived there previously Invasions are increasing in frequency Invasions often result in the arrival of species with strong local ecological effects Invasions eventually homogenize the biota world-wide

33. Properties of Successful Invaders 1 Vector - a means of transport must be available, e.g., ballast water of ships, ability to disperse (e.g., planktotrophic larvae)

34. Properties of Successful Invaders 2 Vector - a means of transport must be available, e.g., ballast water of ships, ability to disperse (e.g., planktotrophic larvae) Invasion frequency - because most arrivals do not result in invasion success, frequency of arrival is important

35. Properties of Successful Invaders 3 Vector - a means of transport must be available, e.g., ballast water of ships, ability to disperse (e.g., planktotrophic larvae) Invasion frequency - because most arrivals do not result in invasion success, frequency of arrival is important Ecological compatibility - invading species need an appropriate habitat in which to colonize and propagate

36. Properties of Successful Invaders 4 Vector - a means of transport must be available, e.g., ballast water of ships, ability to disperse (e.g., planktotrophic larvae) Invasion frequency - because most arrivals do not result in invasion success, frequency of arrival is important Ecological compatibility - invading species need an appropriate habitat in which to colonize and propagate Survival of initial population variation - initial fluctuations of small population size results in extinction of invading species

37. Invasions are Common Ship ballast water has many potentially invading species Transport of commercially exploited mariculture species resulted in transport of other species as well Canals are important routes for invaders. Suez Canal facilitated invasions, mainly from Red Sea to Mediterranean Sea

38. Invaders can have significant effects Periwinkle Littorina littorea invaded New England, USA from Europe. Now most common rocky shore snail and has significant effects on seaweed communities Shore crab Carcinus maenas invaded from northern Europe to become common all over the world Freshwater zebra mussel, Dreissena polymorpha invaded from eastern Europe to North America, has exerted strong effects on water column, and on native mussels

39. Invasion routes of species of the crab genus Carcinus maenas from European waters to sites around the world

40. Conservation Genetics Genetic markers (e.g., DNA sequences, length fragment polymorphisms in mitochondrial DNA) allow identification of populations This allows species identification, identification of different migrating stocks of fishes, turtles, and marine mammals Examples: Green turtle females shown to home to the same nesting beaches, after migrations of thousands of km to feeding grounds; fishing of Loggerhead turtles in eastern Atlantic shown to deplete nesting turtles in Florida; stocks of migrating humpback whales have been identified

41. The End