Threats to biological diversity 3: Exotic Species

1. Threats to biological diversity 3: Exotic Species Vanessa Couldridge & Sam Hopkins Biodiversity & Conservation Biology DepartmentMatteo GarbelottoUniversity of California

2. Introduction • The Invasion Biology course discusses exotic species in detail. • Rather than repeat everything, the following examples of invasive species have been selected for discussion: • Rinderpest • The black rat (Rattus rattus) • The toad/platanna – Xenopus laevis • Chestnut blight

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. History of the Plague • An early example is the plague of Justintian 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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 the habitat disturbed by humans • Have hybridized with Xenopus gilli

22. Chestnut Blight (Cryphonectriaparasitica)

23. The American Chestnut(Castanea dentata)

24. 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)

25. 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

26. “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

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

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

29. 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…”

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

31. 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

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

33. 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

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

35. 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

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

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

38. 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 here from Ichang in 1900. • to hybridize for ornamentals and nut production

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

40. Cryphonectria parasitica: Life Cycle

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

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

43. 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.

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

45. 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

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

47. Like most cankers - fairly specific host range Serious pathogen: American & European (infects Japanese and Chinese much less) Moderate pathogen: Chinquapin & Live Oak  Can also be found infecting/living on numerous oak species in the US Host Range

48. Rate of Spread • Aggressive attempts to halt the spread of the blight were made by PA and NY • removed chestnut over a large area to halt southward spread • In 1911-1913, the U.S. Congress appropriated special funds to enable foresters to study and control the blight

49. Horticulturalists, found a blight-free area in Pennsylvania and quickly imported trees to form an experiment station transported the blight and created a new epicenter Accelerated spread in PA Cuts in funding for Chestnut blight research: With the onset of World War I in 1914 The evident futility of control efforts Rate of Spread

50. By 1926, fungus reported throughout native range • By 1940, virtually all (an estimated 4 billion) were dead or infected with the blight • Chestnut was the dominant wood processed at PA sawmills in the early 1920s, • salvage logging to make use of the dead and dying trees