Lecture 4: species conservation Flashcards
What is a species?
Typological view (old-fashioned)
- changeless, perfect type
- species & subspecies discrete and invariant
- variation unimportant
Population (or evolutionary) view
- focuses on variation within species
- group of individuals expressing genetic,
morphological, physiological & behavioural variation - This is the basis of evolutionary change and adaptation
Rejection of typological view key to Darwin’s insights
Biological species concept (BSC) based on typological
– “Groups of actually or potentially interbreeding populations which are reproductively isolated from other such groups” (Mayr 1942)
– Essential criterion is reproductive isolation, or conversely, the ability to reproduce and therefore exchange genetic material
– also known as the isolation concept
Issues with BSC:
– Difficult to determine reproductive isolation if not sympatric – so spp. Are often judged on surrogate criteria; e.g., morphological measurements
– BSC defined by one set of criteria but taxonomists end up using another – generally morphology
– Doesn’t work for asexual species and taxa within which genetic introgression is common (e.g., plants)
Reproductive isolation mechanisms in BSC:
Reproductive Isolation Mechanisms Considered in the Biological Species Concept
Premating isolation mechanisms:
- Seasonal and habitat isolation (potential mates do not meet)
- Behavioural isolation (potential mates meet but do not mate because of behavioural differences)
- Mechanical isolation (copulation is attempted but transfer of sperm is
unsuccessful)
Post-mating isolation mechanisms:
- Gametic mortality (sperm transfer occurs but ovum is not fertilized)
- Zygote mortality (ovum is fertilized but zygote dies)
- Hybrid inviability (zygote produces an F1 hybrid of reduced viability)
- Hybrid sterility (F1 hybrid is fully viable but partially or completely sterile or
produces deficient F2)
From Mayr 1963.
Phylogenetic species concept (PSC)
– classification should reflect the branching (or cladistic) relationships among species
– relationships described in a cladogram
– a species is ‘the smallest diagnosable cluster of populations with a common paternal pattern of ancestry and descent’
-often uses mitochondrial DNA for diagnosis as this is well conserved within lineages
PSC works well, it deals with sexual and asexual species
But the issue is that it proliferates taxa (subspp. and even races would gain species status)
e.g. Cracraft (1992) applied the PSC to the bird of paradise and described 90 species, up from 40-42 spp. Described under the BSC (genetic differences split taxa that can still interbreed)
Numerous challenges remain on how to define species
Where to draw the lines between species (e.g., chrono-species, whose traits have drifted
over time)?
e.g. see Pied crows and Carrion crows - these crows belong to just two species but are highly morphologically divergent
e.g. crested lark and thekla lark - subtle differences in habitat and song w/limited interbreeding
Conservation focus: should we conserve individual species?
- Should we try to conserve individual species?
– landscape vs. species conservation - Priorities
– listing
– threat criteria
Conservation efforts may be targeted at:
Conservation efforts may be targeted at:
– populations / species
– habitats
– ecosystems
Should we focus on landscape level?
Why focus at landscape level?
Because we don’t even know how many species there are
problems of the species concept:
‘a group of organisms capable of interbreeding to produce fertile and viable offspring, forming a gene pool and sharing common adaptations’
^ this doesn’t imply particular level of uniqueness – which is more important – is the species:
– a critically endangered species in a multi-species lineage
– or a vulnerable species that is the only representative of its genus?
See the EDGE project: Evolutionarily Destinct and Genetically Endangered list
Species/subspecies/ hybrids can be hard to define – which should be conserved?
Species/subspecies/ hybrids can be hard to define – which should be conserved?
E.g. red wolf is a hybrid between coyote and grey wolf – by number it is endangered – but is it an undesireable hybrid that should be culled to protect the genetic integrity of the other species?
E.g. Swift fox – Canadian sub-species if recognised as a species would need to be protected
There are so many threatened species… 1/4 of species assessed by IUCN are endangered
Many species will go extinct before being recognised
conserving habitats/ecosystems can conserve many component species
People and nature
Balancing the needs of humans and nature – Mace (2014)
Timeline of different ways humans have recognised nature over time
Rough timeline
Framing of conservation
Key ideas
Science underpinning
1960-1970
Nature for itself
Species, Wilderness, Protected areas
Species, habitats and wildlife ecology
1980-1990
Nature despite people
Extinction, threats and threatened species
Habitat loss, Pollution, Overexploitation
Population biology, natural resource management
2000 - 2005
Nature for people
Ecosystems, Ecosystem approach, Ecosystem services, Economic values
Ecosystem functions, environmental, economics
2010
People and nature
Environmental change, Resilience, Adaptability
Socioecological systems
Interdisciplinary, social and ecological sciences
BNG (Biodiversity net gain)
The government is taking an environment level conservation approach
Based on a metric developed by Natural England that defines how valuable different types of habitat unit are
Why work at species level ever?
Flagship status
e.g. China’s bamboo uplands
Giant Panda (symbol of wwf)
e.g. Brazil’s Atlantic forests
Golden Lion Tamarind monkey
The general public responds to these charasmatic species
Issues: See Simberloff (1998):
– Flagship species are often very expensive to conserve (extra support may compensate this)
- conservation of different flagship spp. can conflict conserving predatory species can risk further endangering prey species in their territory
Umbrella potential
e.g. Grizzly bear – home range protection would conserve a large area in pristine condition
Issues: protection conferred on other spp. is a “matter of faith” + intensive management interventions are clearly contradictory Just focusing on one species may neglect the overall ecosystem health
Economic / cultural value
e.g. Salmon, cod, ling all of economic resource value
Bears have cultural significance in native people of the Americas
Issue: managing commodities does not equate to managing biodiversity
Nature should not be commodified – economically there are many species ‘without value’ although this is not the case in their ecosystem role value
Advantages of species focused conservation
targeting/monitoring/delivering
- PVAs – population viability analysis
- indicator species e.g. Bittern are an indicator species of reedbed health – their conservation requires healthy ecosystem (umbrella potential with positive effect)
ecosystem stability - keystone species – indicate healthy balance, essential in food web
- rivets and redundancy see Ehrlich & Ehrlich (1981) and Walker (1992)
^ if we interpret the ecosystem as the wing of a plane held together by species ‘rivets’ using a few may not be noticeable but at some point if too many are lost the wing of the plane will fall of
remember: unpredictable consequences of changes in the abundance of individual spp.
Priorities and listing
Listing is necessary to document status
Many national/regional lists
e.g. UK “Birds of Conservation Concern” (2021)
https://www.bto.org/sites/default/files/publications/bocc-5-a5-4pp-single-pages.pdf
^235 birds assessed
– 70 red listed (≥ 50% decline in UK over 25 yrs) farm and woodland species mostly
– 103 amber listed (25 – 49% decline in UK over 25 yrs)
– 62 green listed (least concern) urban areas and woodland species mostly
^ Creating this list identifies areas requiring the most conservation effort
Most comprehensive efforts, international: IUCN Red Data Book
Most comprehensive efforts, international: IUCN Red Data Book: http://www.iucnredlist.org
> 120,000 spp. evaluated
* usually by an IUCN Species Survival Commission taxonomic specialist group
https://www.iucn.org/commissions/species-survival-commission/about/ssc-specialist-group-directory
^ species assigned to 1 of 9 categories based on:
* extent of available information
* population trend
* current threats
for more on criteria see: https://www.iucnredlist.org/resources/categories-and-criteria
*clear, quantitative framework -though necessarily flexible to remain relevant to all species’ situations (Mace et al. 2008)
*clarifies problems and threats
* network of over 9,000 scientists
* independent peer review (Lamoreaux et al. 2003)
– identifies required actions
– motivates conservation
(ordinal) categories defy objective analysis
- shouldn’t be used for priority setting (Possingham et al. 2002)
- rather, priorities should be based on ROI (we’ll return to this later in course)
however, probability of recovery is hard to establish, except for well-studied examples
hence, prioritisation remains highly subjective and contentious - whole ethos may be at odds with triage (Marris 2007) – but see Bottrill et al. (2008)
Landscape vs. species conservation summary
– each has pros & cons
– need to remain flexible
– integrate both according to need
– towards “rivet” end of the scale, so can’t afford to neglect individual species altogether
Overall summary
- Species concepts: Biological, Phylogenetic, Evolutionary – can affect conservation actions
- How many species? – only c. 2 million named - but probably c. 10 million in total
- Arguments for and against species-focused conservation – but most practitioners (as opposed to academics) remain species-focused
- Spectrum of viewpoints from the rivet to the functional redundancy extremes – reality is probab in between but loss of individual species can have unforeseen consequences
- Listing species by threat category has been a major tool for focusing and prioritising efforts
– now strongly criticised …
– but alternatives not yet widely available for many species
