Ecology and Conservation - Tropical Rainforests

How is biodiversity distributed?

• Biodiversity is not equally distributed

  • There are more diverse than others

    • e.g. Tropical rainforests – cover ~7% of world’s surface but are home to over half of terrestrial species including invertebrates and vascular plants

  • Species richness varies between different areas

Studies of Alfred Russel Wallace

• Studied the distribution and diversity of plants and animals, mainly in SE Asia

  • Showed that geographic barriers (rivers and mountains) marked the boundaries of many species’ ranges

  • Found that places with similar climates did not always have the same species and so deduced it was a record of inheritance

• Marked transitional zone between Asia and Australia (Wallace’s Line)

  • Determined biogeographic realms based largely on the distributions and taxonomic relationships of particular vertebrate families.

Describe major biogeographic distributions.

• Cosmopolitan

  • State of being found almost anywhere around the world

  • E.g. Drosophila melanogaster, brown rat, common rock pigeon, house dust mite

• Endemic

  • Unique to a defined geographical location

  • E.g. lemurs in Madagascar and silverswords in Hawaii

• Disjunct

  • Distribution with gaps

  • Disjunct distributions usually fall into one of a fairly small number of patterns

  • Araucaria pine (South America and Australasia)

  • Alligator (North America and China)

How are ecological niches determined?

• Fundamental niche space - the set of environmental and biotic conditions necessary for the existence of a species

• Realised environmental space - the set of conditions actually available within the resource space

Define phylogenetic niche conservatism.

• Tendency of species to retain ancestral ecological traits over evolutionary time

• Closely related species tend to occupy similar ecological niches and maintain similar environmental preferences due to their shared evolutionary history.

• e.g. Treefrogs

  • Less diverse in the temperate zone than in the tropics

  • Only a few lineages have recently adapted to the temperate zone

Name and describe historical factors that affect geographic distributions.

• Extinction of some populations of a species, or of some species of a higher taxon

• Dispersal

  • Expansion through favourable habitat or jump dispersal across unfavourable habitat

• Vicariance

  • Populations of a widespread species are separated due to barriers resulting from changes in geology, climate or habitat - leads to divergence and speciation

• Composition of regional biota

  • Geographic history of a clade is often complex and may include both vicariance and dispersal events at different time periods

Describe how tropical forests are classified.

• Tropical moist broadleaf forests (tropical rainforests)

  • High levels of rainfall (>2000 mm annually), low variability in annual temperature, characterised by dipterocarps

  • High biodiversity

• Tropical moist deciduous forest (monsoon forest)

  • Low variability in annual temperature

  • Dry season 3-6 months, rainfall 1000-2000 mm annually

  • Mostly deciduous/semi-deciduous – heavily impacted by teak logging in SE Asia

• Tropical dry forests

  • Long dry season (5-8 months), rainfall 1000 - 1500 mm, so deciduous trees predominate, very sensitive to burning

• Tropical and subtropical coniferous forests

  • Found at high altitude, lower biodiversity but high endemism

What is the Latitudinal Biodiversity Gradient (LBG)?

• LBG - Ecological pattern that describes how biodiversity tends to decrease as one moves from the equator toward the poles

• Hypotheses for LBG

  • A. Higher rates of speciation in the tropics (cradle hypothesis)

  • B. Less extinction in the tropics (Ark)

  • C. Higher rates of speciation and lower rates of extinction in the tropics with high species migration out of the tropics

• There is no relationship between diversity and LBG

Define molecular ecology.

• Use of molecular genetic tools to study ecological questions

• Assess genetic diversity within individuals, populations, species

• Assess genetic differentiation among individuals, populations, species

Name some molecular markers

• Allozymes

• Microsatellites

• Mitochondria DNA

• Nuclear sequences

• Single nucleotide polymorphisms

• Whole genomes

Positive and negative using mitochondrial DNA as markers.

• +ves:

  • Maternally inherited

  • No recombination

  • Multiple copies – easy to amplify

  • Offer a high mutation rate so more variation

• -ves:

  • Genetic introgression between closely related species

  • Copies can move to the nuclear genome and form pseudogenes

  • Only gain information on maternal side

Compare genotype and haplotype in diploids.

• Genotype – full genetic composition of an individual or of a particular region

• Haplotype – set of linked genetic information along a chromosome

  • Directly sequenced from mtDNA

    OR

  • Resolved from genotypes composed of two alleles

Examples on how to sample genomic DNA

• Tissue

  • Toe clippings – used on amphibians

  • Ear clips

  • Blood

  • Wing punches – used on bats

• Non-invasive techniques

  • Buccal swabs

  • Faecal swabs

  • Hair traps

  • Museum samples

Describe PCR processes.

• Denaturation – high temperature cause DNA to unravel

• Annealing – primers added and bind to specific parts of the DNA

  • Done at lower temperatures to allow hydrogen bonds to form

• Extension – DNA polymerase at 70⁰C to extend chain

What does DNA barcoding aim to do?

• Uses short DNA sequence of the mitochondrial cytochrome c oxidase gene

• This region has sufficient mutational differences to distinguish animal species

• Small amount of tissue is needed but it is valuable to have reference ‘voucher specimen’ material

• Barcode sequences of similar taxa are compared to each other

• Particularly useful for poorly studied taxa (e.g. insects)

Limitations of DNA barcoding

• Overlap between inter- and intraspecific genetic variation

• Mitochondrial introgression

• Variable mutation rates across different taxa

• High divergence can accumulate quickly in bottlenecked populations

What is the rainforest refugia hypothesis?

• Pleistocene glacial periods, Amazon rainforest was fragmented

• Allopatric fragmentation of species in refugia → greater genetic diversity and increased speciation

• Hypothesis largely rejected for Amazon but can be applied to Africa and SE Asia

Define phylogeography.

The field of study concerned with the principles and processes governing the geographic distribution of genealogical lineages, especially those within and among closely related species

Consequences of periodic glaciations in northern latitudes

• Cooler and drier during Ice Ages

• Several refugia

  • E.g. Iberia, southern Italy and Balkans

• Greater genetic diversity in the south than the north

Compare effects of interglacial and glacial regions

During the interglacial periods:  High sea levels  High levels of precipitation  Decreased aridity  Spread of tropical forest across mainland and island regions

During the glacial periods:  Low sea levels  Reduced levels of precipitation  Increased aridity  Replacement of tropical forest    by grassland and savannah

Define umbrella species. Why should conservation efforts be focused on them?

• Large-bodied and wide-ranging animals that require a large area of suitable habitat

• Conserve an area to protect flagship species (e.g. tigers, panda) which in turn protect the rest of the ecosystem

Define keystone species. Why should conservation efforts be focused on them?

• Species that plays a disproportionately large role in supporting the ecosystem of which it is a part

• E.g. sea otters help to maintain kelp ecosystems

Define sentinel/indicator species. Why should conservation efforts be focused on them?

• Ecology and sensitivity to environmental change

• Show when conditions are changing therefore useful for conservation efforts.

• e.g. lichen, amphibians

Example of a keystone species. What effect do they have on their ecosystem?

• Black-tailed prairie dogs

  • Prey for many species

  • Their burrowing activity = aeration of soil

  • Eat plants (creates grazing pressure) which improves plant production

Define evolutionary significant units (ESUs).

Group of populations with a common evolutionary history

Define management units (MUs).

Result of more recent isolation; differ in allele frequency due to lack gene flow

Is it important to conserve sub-species?

• Yes, but argument to say we don’t need to protect them all

• e.g. 6-8 sub-species of cactus wren; molecular data shows there are only two distinct genetic species

• e.g. green turtles in Africa, mitochondrial DNA shows there are two evolutionary significant units (ESUs)

Case study - Elephants of Borneo

• Hypothesis - Introduction from India so genetically similar

• Molecular data suggests Bornean elephants genetically distinct and should be recognised as ESU

• Reject the hypothesis of recent introduction from India

• Supports the hypothesis of Pleistocene colonisation of Borneo followed by isolation

• Indicates high conservation priority for Bornean elephants

What did Norman Myers propose in 1998?

• Conservation priorities based on geographical distribution of biodiversity

• Identified 25 biodiversity hotspots

  • High diversity and endemism

  • Must contain at least 0.5% or 1,500 species of vascular plants as endemics

  • Must have lost at least 70% of primary vegetation

• Suggested these should be the focus of conservation efforts

What concept did Russell Mittermeier introduce?

• Concept of major tropical wilderness areas (high endemism and pristine) that should also be high priority for conservation

• Major wilderness areas where low human population density

Define an ecoregion.

• Ecoregion - large area of land or water that contains a geographically distinct assemblage of natural communities that:

  • Share a large majority of their species and ecological dynamics

  • Share similar environmental conditions

  • Interact ecologically in ways that are critical for their long-term persistence

What is the Global 200?

• The WWF has identified 200 priority ecoregions (terrestrial, freshwater, and marine) of the planet that can serve as a unit for conservation

• These ecoregions have distinct or high (species richness or endemism) biodiversity

• Conservation of these ecoregions would save most of the diversity of the Earth’s ecosystems

What is the Global Deal for Nature?

• Take an ecoregion-based approach to protect and interconnect 50% of the terrestrial realm by 2030

• The target set by the CBD for 2020 was 17% protected

• Would require increased habitat protection and restoration, national- and ecoregion-scale conservation strategies

• Integral to the deal should be the empowerment of indigenous peoples and local communities.

Define island biogeography

• Island biogeography – explains species richness of island where island is an isolated ecosystem

• e.g. actual islands, mountains in deserts, protected areas in a ‘sea’ of unsuitable habitat

• Complex interactions between processes of immigration, colonisation and extinction

• Aspects of the island, such as topology, size, orientation, substrate lead to variation in these processes

• Theory that insular biota maintain a dynamic equilibrium between immigration and extinction rates

• Islands with highest species richness are large islands close to the mainland

Considerations on where to put protected areas

• Size - bigger is better

• Edge effects

• Random events and SLOSS (Single Large or Several Small)

• Migration and corridors

Why does size need to be considered for protected areas?

• Bigger is better as it subject to fewer edge effects

• Able to support larger population size, allows for greater genetic diversity

• Able to support more species which are less likely to go extinct

• Larger reserves more likely to have a wider range of habitats and zones of use

• Less susceptible to natural or anthropogenic disturbance

Why do edge effects need to be considered for protected areas?

• More likely to have:

  • Lower habitat quality

  • Invasions of exotic or edge species

  • Different microclimate (e.g. drier/windier/sunnier)

  • Avoidance by ‘interior’ species (e.g. tigers)

Why do random effects and SLOSS need to be considered for protected areas?

• Environmental catastrophes happen – natural or man-made which can be dangerous if there is risk of extreme weather or other events

• e.g. Reintroduction of Governor Laffan’s fern to Bermuda is difficult as hurricanes keep killing the replanted individuals

• Better to do it in several caves rather than one to avoid all the individuals being killed

Why do migration and corridors need to be considered for protected areas?

• Matrix – space between reserves

• Connectivity between reserves depends on permeability of the matrix which depends on:

• Inherent dispersal capability of the species

• Matrix quality

  • e.g. how dangerous is it to dispersal species (e.g. roads, human hunters),

  • e.g. urban landscapes, that inhibit some species from entering it?

Case study: assessing optimal placement for forest corridors for red panda in Bhutan

Considerations:

• Look at where that potential habitat occurs in current land use – could be in timber extraction zones (puts at risk)

• Then predict corridors that’s most cost effective and identify pinch points (potential problems)

Conclusions:

• >75% predicted potential habitats for red pandas are outside core zones

• Livestock grazing and presence of dogs (disease, hunting) need for future study of these impacts. Overall negative impact on populations

• Habitat and connectivity modelling indicates need to maintain/extend corridors for red panda dispersal both within Bhutan and to neighbouring Arunachal Pradesh in northeast India

Do protected areas work?

• Most parks are successful at stopping land clearing

• They can also mitigate (to some extent) logging, hunting, fire, and grazing

• How effective a park is depends upon the level of management activities

  • e.g. enforcement, boundary demarcation, and direct compensation to local communities

• Increased funding would increase the ability of parks to protect tropical biodiversity

Examples where protected areas don’t work.

• 69 species of large mammals in 78 African protected areas

  • The index reveals on average a 59% decline in population abundance between 1970 and 2005

• Global forest loss has steadily increased in recent decades

  • Forests in PAs have lower rates of loss that non-protected forests but the deforestation trends over time are similar between protected and non-protected areas

• In the global tropics loss of forest is typically for agriculture

• In northern latitudes forest loss is more often due to wildfires, pests and storm damage

Describe fortress conservation. Give an example.

• Belief that biodiversity protection is best achieved by creating protected areas where ecosystems can function in isolation from human disturbance

• e.g. Yellowstone

  • Created using violent exclusion and extermination of native Americans

  • Racist ideals allowed people to ignore the rights of indigenous people. ‘White man’s burden’

What’s the issues with ‘wildernesses’?

• Binary - only considers people and nature

• Wildernesses are understood as ‘terra nullius’ – untouched, unchanging and outside of human history

• Ignores environmental influence of earlier indigenous land users – e.g. foraging, domestication and planting

Define colonialism.

• The establishment, maintenance, acquisition and expansion of colonies in one territory by people from another territory

• A lot of protected areas were founded by colonial powers

Define neocolonialism.

• The practice of using capitalism, globalisation, and cultural forces to control a country in lieu of direct military or political control

• This model continues to dispossess and harm people today

Example of disenfranchisement of indigenous people.

• Ogiek continue to be evicted illegally from their ancestral lands in the Mau forests of Kenya

• July - October 2020: Kenya Forest Service has evicted 1100 Ogiek people from the Mau Forest

• Forest is being destroyed by plantations, agriculture, wood harvesting, grazing, infrastructure (e.g. dams)

• Land tenure rights given to many people not indigenous to the area

Has removing people conserved areas? Ethics?

• Over 100,000 protected areas where people have restricted access and use - these cover ~17% of the earth’s land area.

• Colonial and post-colonial governments have removed people from areas they were living in.

  • Cause conflict and infringes the rights of local people.

• On the other hand, excluding people appears to have protected habitats (often by reducing deforestation) and protected biodiversity.

  • Move towards community-based conservation, directly involving local people in conservation with the combined aim to relieve poverty.

• Choice between law enforcement and provision of other economic activities

Describe nature-friendly human-modified forest landscapes

• Should contain ≥ 40% forest cover. Configured with:

  • ~10% in a very large forest patch

  • Remaining 30% in many evenly dispersed smaller patches and semi‐natural treed elements (e.g. vegetation corridors)

• The patches should be embedded in a high‐quality matrix