Threats to biological diversity 3: Exotic Species

1. Threats to biological diversity 3: Exotic Species Lecturer: James Reeler Material by: Sam Hopkins & Vanessa Couldridge BCB 341: Principles of Conservation Biology

2. Introduction • Invasion by alien species can have a significant impact on biodiversity • Usually there are few predatory species/diseases for successful invaders (competitive advantage) • Exacerbated by habitat destruction/disturbance • Possibly exacerbated by climate shifts – expansion into new suitable ranges • Primary contemporary cause – humans • Deliberate (plants/animals with economic/aesthetic uses) • Accidental – “piggybacking” on other species

3. Invasion – who? • Not all species that are transported to new areas become invasive. • There are several characteristics of good invaders: • High reproductive rate (quickly build up a large population under favourable conditions) • Generalist species (variable diet, no strong habitat requirements) • Good dispersers (can rapidly spread to new areas & find suitable habitats)

4. Invasion – where? • Certain areas are more vulnerable to invasion • Disturbed areas/early succession • Tend to have unexploited resources/empty niches • Little competition • Remote islands with low diversity • Simple food webs/empty niche space • Remote islands/fragments with no predators • Often naive prey (included plants poorly adapted to herbivory

5. Invasion – how? • Generally follows three stages: • 1. Usually start with a few individuals • High initial likelihood of population extinction • Initial establishment phase – growing population, little size expansion • 2. Spreads from initial site and increases range (expansion phase) • 3. Fills all available habitat and enters saturation phase.

6. Case studies • The following examples of invasive species have been selected for discussion: • Rinderpest • The black rat (Rattus rattus) • The toad/platanna – Xenopus laevis • Chestnut blight

7. Rinderpest • Viral disease that affects primarily cattle (also known as cattle plague) • All cloven-hoofed wild and domestic are animals susceptible to the disease • Belongs to the genus Morbillivirus • Affects gastrointestinal and respiratory systems • Highly contagious and usually fatal; it can wipe out entire populations • Death occurs 6-12 days after the first symptoms http://www.virology.net

8. Rinderpest: Introduction to Africa • Introduced to Africa from Asia in 1887 • Disease was present in Indian cattle imported to the east coast of Africa to feed the Italian army, which was invading Ethiopia at the time • Quickly spread to local cattle and wildlife populations • From there the disease swept across eastern and southern Africa, with devastating consequences • Within 10 years it had reached South Africa

9. Rinderpest: Spread in Africa • This map shows the spread of the disease across the African continent • The fauna and flora of Africa south of the Sahara changed completely as a result

10. Rinderpest: Plague of 1890s http://www.Aleffgroup.com • Millions of animals died, both wild and domestic • Reports indicate more than 90% of cattle and wildebeest were wiped out

11. Rinderpest: Devastation Caused • Wildlife killed by rinderpest included wildebeest, buffalo, giraffe, warthog, eland, kudu, and other buck species • Predators also suffered as their prey species disappeared; lions reportedly became man-eaters • Pastoralists depending on cattle for their livelihood faced severe hardship and death • Ox-wagon transport was brought to a standstill • Loss of grazers transformed the landscape

12. Rinderpest: Control • The disease was eventually brought under control through early attempts at vaccination and natural immunity among surviving animals • In the early 1960s a more reliable vaccine was developed and between 1962 and 1976 there was a large-scale attempt to eradicate rinderpest entirely from Africa through mass vaccination • This was largely successful – 15 out of 17 countries were freed of the disease • Outbreaks still occur from time to time, but none as severe as the original plague of the 1890s

13. Rinderpest: Recovery • Vaccination of cattle in the 1960s eliminated rinderpest from wildlife populations, as cattle could no longer act as a reservoir for the disease • Wildebeest numbers in the Serengeti increased by about six-fold over a period of 15 years; Buffalo numbers also increased dramatically http://geoimages.berkeley.edu

14. Rinderpest: Landscape Change 1980 2003 • This had an impact on the environment by changing grassland into woodland – an increase in grazers eliminated the fuel for fires that control tree growth. Fires are now less frequent and do not burn as hot http://www.circa.gbif.net/Public/irc/gbif/pr/library?!=/ science_symposia/2006/mduma_ppt/_EN_1.0_&a=d

15. Rinderpest and Canine Distemper • Ironically, it has been suggested that eradication of rinderpest has led to an increase in canine distemper among lions • Lions feeding on wildebeest infected with rinderpest may have gained immunity to canine distemper, since the two viruses are very similar to each other (both Morbilliviruses) http://www.eecs.umich.edu

16. The Rat1 • The Black Rat (Rattus rattus) was originally from Asia • It made its way to the near East in Roman time • It was in Europe in the 8th century • From Europe it had a boat ticket to the rest of the world • Rats are nocturnal • Rats are omnivorous • They are good breeders

17. The Rat and the plague2 • The rat and a number of other rodents are largely responsible for out breaks of plague through history • Humans as carriers of rats also participated in the spread of the disease • Often the rats would then infect native rodents with the disease

18. History of the Plague • An early example is the plague of Justinian 3 • 544, The first great plague 4 • 1348, Black Death 5 • 1665, Great Plague 6 • 1899, Plague in South Africa 7 • Recent plague – 2005/ 2006 DRC 8,9

19. Other effects of rat invasion – Lundy Puffins 10, 11 • Lundy island is off the coast of North Devon, UK • Rats reached the island 200 years ago • Rat numbers reached 40,000 • Extermination started in 2003 • Puffin and Manx Shearwater numbers had declined • Now rats gone, hopefully bird numbers will increase

20. Other effects of rat invasion – Pacific Islands 12,13 • Reached Pacific Islands in the 17th century • Now established on 28 groups of islands • Eat native snails, beetles, spiders, moths, stick insects, and fruit, eggs and young of birds • Largest threat to the Rarotonga flycatcher • Other Island birds affected • Sooty terns, Seychelles • Bonin Petrels, Hawaii • Galapagos dark-rumped petrels Galapagos islands • White tailed tropic birds Bermuda

21. The Toad –Xenopus laevis 14 • Xenopus laevis is the common platanna in Southern Africa • It is mainly aquatic • Females reach 130 mm • Eats insects, small fish, young and larvae of its own species or other species of frogs • Adults can breed more than once per season

22. The Toad –Xenopus laevis 14 • Xenopus laevis is found about the world owing to • Lab animals • Pet trade • Pregnancy tests • These animals escape and can form viable populations • Now found in USA, Chile, Mexico, France, Indonesia and the UK • These frogs are a great invader owing to • Good in disturbed environments • Has a varied diet • High reproductive rate • High salt tolerance • Disease resistant • Can move overland or through rivers and streams

23. The Toad –Xenopus laevis 14 • Xenopus laevis are a problem because they • Predate upon and compete with native species • Are toxic to predators • Make water turbid

24. The Toad –Xenopus laevis • Seen in Southern California • X. laevis has been present since the 1960s • Preys on the Tide Water Goby • Preys on the Endangered Red-legged frog • Also managed to establish parasites that need alternate hosts 15 • In South Wales, Xenopus were found to have a very varied diet ranging from zooplankton to bank voles to Xenopus eggs 16

25. The Toad –Xenopus laevis 17 • In South Africa X. laevis is an invasive • Animals are moved out of their natural range by fisherman • Animals make use of habitats disturbed by humans • Have hybridized with Xenopus gilli

26. Chestnut Blight (Cryphonectriaparasitica)

27. The American Chestnut(Castanea dentata)

28. American Chestnut: Range • Maine to Georgia and west to Ohio and Tennessee. (Braun, 1950) • Commonly made up 25% or more of mixed stands • Formed pure stands on many dry Appalachian ridgetops and near densely populated areas. Map of Historical Range of Castanea dentata (Saucier, 1973)

29. Common on midslopes and other moderately dry soils • Shared moist meso-phytic soils with many other species • Tap root 4 to 5 ft down American Chestnut: Habitat

30. “Redwoods of the East” • Mature chestnuts could be 600 years old and average up to five feet in diameter and 100 feet tall • Many specimens of 8 to 10 feet in diameter were recorded

31. American Chestnut: Ecological Importance • Wildlife depended on the abundant crop of chestnuts • Many species of insects fed on the leaves, flowers, and nuts

32. American Chestnut: Economic Importance • Throughout much of the range chestnut had the most timber volume of any species • It was half the standing timber volume of CT • Was the major source of tannin for leather pro-duction (6-11 % tannin content) • Chestnuts

33. Fast growing -reached half ultimate height by 20th year • Resistant to decay • Straight and tall - often branch free for 50 feet • Only white pine & tulip poplar could grow taller “From cradle to casket…”

34. “From cradle to casket…” • Posts & railroad ties • Telephone poles (65 feet) • Construction • Fuel • Fine furniture & musical instruments

35. Scientific forest management in the US was just getting started when the country lost its most important hard wood species (Smith, 2000) • Foresters had begun to develop comprehensive plans for intensive management American Chestnut: Economic Importance

36. Near densely populated areas Chestnut often formed nearly complete stands • due to rapid growth from stump sprouts • repeated coppicing for fuelwood

37. Pure stand of Chestnut in CT 90 years after clear-cutting, 1905. • Experts estimate that American Chestnut represented half the commercial value of all Eastern North American hardwoods

38. “… the most valuable and usable tree that ever grew in the Eastern United States.”

39. Introduction of Cryphonectria parasitica • In 1904, Herman Merkel, a forester at the New York Zoological Garden, found odd cankers on American chestnut trees in the park

40. Introduction of Cryphonectria parasitica • "rapid & sudden death of many branches stems & trees"

41. Introduction of Cryphonectria parasitica • American Chestnut produces a sweet but small nut  • Chinese chestnut produces a large but generally tasteless nut

42. Introduction of Cryphonectria parasitica • Thomas Jefferson • imported European or Spanish chestnut (Castanea sativa) • grafted it onto native root stocks at Monticello. • In 1876, a nurseryman in Flushing, NY, imported the Japanese chestnut (C. crenata). • More were brought over in 1882 and 1886. • Chinese chestnut (C. Molissima) was brought across from Ichang in 1900. • to hybridize for ornamentals and nut production

43. Cryphonectria parasitica • Ascomycete • Produces both conidia & ascospores • Pycnidia stromata break through the lenticels and produce conidia and perithecia producing ascospores are formed

44. Cryphonectria parasitica: Life Cycle

45. Animals and insects • Ascospores are shot into the air after rain storms in the fall • Rain (conidia) Dispersal

46. Infects trunk and branches • Only above ground parts of trees active growth & sporulation

47. How does it kill the tree? • Enters through fissures or wounds in the bark • Grows in and under the bark, girdling the cambium. • Kill the tree above the point of infection.

48. Causes swollen or sunken orange-colored cankers on the limbs and trunks of the chestnut trees.

49. How does it kill the tree? • The leaves above the point of infection die, followed by the limbs. • Within two to ten years the entire tree is dead. • Not uncommon to find many cankers on one tree

50. How does it kill the tree? • The fungus has girdled the tree and is producing yellow conidia asexual spores