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BIOL 2600 > Week 9: Species, Speciation and Extinction > Flashcards

Week 9: Species, Speciation and Extinction Flashcards

1
Q

How many species are there?

A

2 million species described - estimate 5-10 million

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2
Q

Describe mosquito speciation in underground London

A

Culex pipiens - above and underground - morphologically similar but behaviourally different in feeding and breeding patterns - no gene flow in nature - in lab - hybrid cross produced no viable offspring.

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3
Q

What is the species problem?

A

1) how to define a species 2) how to identify species in nature and delineate boundaries between them?

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4
Q

What are the 5 main species concepts?

A

evolutionary, phenetic, biological, ecological, phylogenetic.

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5
Q

Describe evolutionary species concept

A

a lineage of populations which maintains its identity from other lineages and which has its own evolutionary tendencies and historical fate.

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6
Q

Describe phenetic species concept

A

delineates species based on phenotypic similarity. Pros - can be used on extinct species (using fossils), can use genetic data in similar way. Cons - doesnt include evolutionary history (traits could be same due to convergent evo and not due to shared evolutionary history), fails when within-species variation is high or between-species variation is low.

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7
Q

Describe biological species concept

A

delineates species based on reproductive isolation. Species are groups of actually or potentially interbreeding populations which are reproductively isolated from other such groups. If two individuals breed and produce fertile offspring - they are same species. identifies mechanism of speciation to be patterns of gene flow. Cons - extinct species, asexual species, hybridization events.

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8
Q

Describe ecological species concept

A

delineates species based on niche. Individuals of same species compete most closely with each other. Evolution is underlying mechanism (need to get away from competitor - evolve new niche). Pro - can be used for asexual species - possibly for extinct species. Con - doesnt work well on species with different morphs.

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9
Q

Describe phylogenetic species concept

A

based on shared evolutionary history - members of species share common evo history and common fate - distinct from other species. The smallest monophyletic group distinguished by a shared derived character. Puts a scale on species delineation - all mammals have fur and mammary glands but mammals are not all same species. Cannot use polymorphic traits - wont form a clade (ie. flower colour), can use shared derived traits (by definition). Concept may delineate too finely based on shared derived traits.

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10
Q

Describe Cattail case study

A

Broad-leaf (Native), Narrow-leaf (non-native), hybrid cattail (hybrid).

Biological SC - F1 hybrids readily formed, hybrids are fertile but it is reduced compared to parents. Once formed, hybrid has greater clonal growth than parents

Phenetic SC - They do delineate based on morphology of leaf width - also height, gap, spike width and spike length.

Ecological SC - share niche based on water depth

Phylogenetic SC - T. latifolia is monophyletic, T. angustifolia is paraphyletic or polyphyletic

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11
Q

Why do species concepts matter?

A

Why species concepts matter - use taxonomy to make conservation decisions, one of first criteria for COSEWIC is “is it taxonomically valid”, for eastern wolves, it is a public opinion, currently Canis Lycaon cf. - cf means things are complicated

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12
Q

What are modes of speciation based on?

A

Biological species concept - reproductive isolation; caused by genetic divergence

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13
Q

What are the 3 modes of speciation?

A
  1. Allopatric - speciation in different places - geographically isolated
  2. Parapatric - speciation in populations adjacent to each other
  3. Sympatric - speciation in same place.
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14
Q

What is the vicariance model of allopatric speciation?

A

one very large pop subdivided into two large populations. Drift unlikely due to large size of subpopulations - different selective pressures.

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15
Q

What is the peripheral isolate model of allopatric speciation?

A

division of populations that are diff sizes - one large and 1+ small. Founder effects and drift occur in small subpops - still different selective pressures.

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16
Q

What is an example of allopatric speciation?

A

Example: Vicariance in Alpheus shrimp - Isthmus of panama creates physical barrier between seas. Species from opposite sides formed sister species. Mating yielded 1% viable offspring between sister species vs. 60% within sister species.

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17
Q

What is parapatric speciation?

A

Speciation in absence of geographic barrier. Diverging populations form a cline - spatial gradient the frequency of phenotypes or genotypes. Different selective pressures along the cline. Gene flow between diverging populations results in hybrid zone. Hybrids usually selected against - not well suited to live anywhere on cline.

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18
Q

What is an example of parapatric speciation?

A

hybrid zone in sweet vernal grass - grows on mine - soil contaminated with lead and zinc - grows on adjacent pasture where soil is not contaminated. Some gene flow between pasture and mine - interpopulation hybrids - not much. Pasture plants outcross more, flower earlier. Mine plants highly selfing. Differences in reproductive traits greatest closest to pasture-mine boundary.

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19
Q

What is a ring species?

A

populations connected in a circle/ring. Evolved directionally such that those at the ends have no direct gene flow. ie. salamanders in Cali

20
Q

What is sympatric speciation? What drives it?

A

Divergence with geographic overlap - no geographic boundary. ie. cichlids in Nicaragua’s Lake Apoyo. Hypothesis that arrow cichlid evolved from ancestral population of Midas - supported by phylogeographic, genetic, ecological and morphological evidence.

Resource competition model - competition drives it.

21
Q

What happens when incipient species comes back into contact? How does it reinforce reproductive isolation?

A

Reinforcement and secondary contact.

Secondary contact and low hybrid fitness reinforces reproductive isolation.

22
Q

What is reproductive character displacement?

A

when reproductive traits are most dissimilar between species in areas of overlap (sympatry). If hybrids at a disadvantage, ability to mate with other species should be most strongly selected against where hybrids most likely to form ex. reproductive character displacement in snails.

23
Q

What are reproductive isolating mechanisms?

A

prezygotic (before fertilization - deter or prevent mating, prevents fertilization, mechanical, temporal, behaviour, habitat). Postzygotic (after fertilization - deter or prevent viable offspring from being born, lack of hybrid variability, infertile offspring).

Example: isolation through pollinators - many plant-pollinator relationships are obligate - one pollinator for one plant. Reproductive isolation between plant species due to specialist pollinators. Different flower shapes, pollinators, limit gene flow between species.

24
Q

What are the genetics of reproductive isolation?

A
  • Isolation through changes in chromosome number (ploidy)
  • Isolation via Dobzhansky-Muller incompatibility
  • Isolation through Haldane’s rule
  • Ploidy - error in meiosis yield unreduced gametes. Species with different ploidy levels can often interbreed but hybrids are sterile. Common in plants - self-fertilization while waiting for viable mates - increased ploidy = larger cells, larger seed sets and larger pollen grains.
  • Dobzhansky-Muller Incompatibility - Reproductive isolation is result of negative interactions between alleles that arose in diff genetic backgrounds - hybrids selected against because alleles from parent - postzygotic - species (or pops) incompatible - maintains reproductive isolation between parent species (or pops).
  • Haldane’s Rule - Among hybrid offspring - if one sex is rare or sterile it is the heterogametic sex. The heterogametic sex is at a fitness disadvantage - creating a bias for reproductive isolation
    Copious evidence supports idea
    Example: almost all surviving hybrid howler monkeys are female (homogametic sex).
25
Q

What is Scala Naturae?

A

Historically extinction what thought to be impossible - Scala Naturae - Great Chain of Being - extinction not accepted in 1700s

26
Q

What were the first fossils assumed to be?

A

Humans found fossilized teeth from L’animal de l’Ohio and American Mastodon - believed their were from animals that were still alive.

27
Q

What did George Cuvier do?

A

demonstrated that African and Indian elephants were distinct species. Fossilized bones from mastodons were from a distinct species that no longer existed. 1790’s - proved animals could go extinct (expert in skeletal anatomy - conducted detailed comparisons of fossil animals with extant ones)

28
Q

What is the concept of extinction?

A

species becomes extinct when all individuals have died out and left no living descendants. When extinctions occur - phylogenetic diversity lost can vary. Ex. tuatara lizard shares similar features to iguanas but represents a very deep node of only two species - loss would be significant phylogenetic diversity loss.

29
Q

What does the fossil record give?

A

History of life on Earth

30
Q

How are fossils dated?

A

up to 75,000 ybp radiocarbon dating is reliable. 14C isotope decays to 14N at a constant rate. Every 5730 years, half of the 14C will decay in 14N (half-life). After death - no more uptake of 14C so the ratio of 14C/14N gives estimate age.

31
Q

What is background extinction?

A

rates aren’t that high -

  • 95% of all extinctions are due to them
  • Caused by predation, competition, disease, combo of factors.
  • Endemic - native to only one area - extinctions more common
  • Endemic hotspots - regions that have numerous endemic species.
32
Q

What is predator induced extinction as a subtype of background extinction?

A

145-66 mya bivalve family Inoceramidae were prominent - then they went extinct with timing consistent with rise of brachyuran crabs (expert shell crushing predators that went through a radiation event), thought to be only animal capable of creating marks on bivalve fossils - currently 7000 species of brachyuran crabs.

33
Q

What is invasive predator extinction as a subtype of background extinction?

A

feral cats have contributed to extinction of 60 species - leading cause of death for birds in Canada.

34
Q

What is predation on islands as a subtype of background extinction?

A

introductions on islands have large impacts - ecological balance upset - potential for unintended downstream impacts.

35
Q

What is introduced predators and island extinctions as a subtype of background extinction?

A

rats introduced to 80% of global island groups - responsible for extinction of at least 100 insular species.

36
Q

What is competition and extinction as a subtype of background extinction?

What did Andrew Knoll do?

A

Evolutionary lineages with improved adaptive traits can lead to competitive exclusion.

Ex. NS for plants better adapted to capturing and processing sunlight and/or transporting water and key nutrients

found overlap between dominant species in decline and new species that replace it as the dominant species. The new species has adaptations that allowed improved light capture and nutrient transport

37
Q

What is disease and extinction as a subtype of background extinction?

A

chytridiomycosis in amphibians in 2000s - caused by chytridiomycete fungus - interferes with ability to transport chemicals across epidermis - wiped out 30 species in Panama and problem in Australian rain forest.

38
Q

What is compounding effects and extinction as a subtype of background extinction?

A

two waves of human colonization of Hawaiian islands - 4000-1500 years ago from East Indies and 1500s from Europe.

90-110 of 125-145 bird species extinct since. Compounding effects of disease introduction, predator/competitor introduction and hunting by humans.

39
Q

What is mass extinction?

A

> 50-75% of species lost across all major taxa across broad geographic range - caused by widespread phenomena - climate change, meteor strike etc.

  • At least 5 - maybe 8 over past 600 my
  • Some wiped out 90% of species
  • Most agree 6th mass extinction is occurring
40
Q

What are the Big 5?

A 
Crustaceous (aka K-Pg) (~65 mya)
Triassic (~200 mya)
Permian (~250 mya)
Devonian (~375 mya)
Ordovician (~450 mya)
41
Q

Describe the crustaceous

A

Most recent mass extinction

50% of all genera disappeared including dinosaurs

Iridium (rare on earth but common in asteroids) in rock layers at K-Pg boundary

Caused by impact of 10 km diameter asteroid - caused particulate in air - blocked sun.

42
Q

Describe the permian

A

Largest mass extinction - 90% of all animals went extinct - land and sea.

Thought to be caused by massive volcanic eruptions in Siberia - caused increase in Co2, global temp increased by 6C, increase in ocean acidity

Organisms adapted to low oxygen levels survived.

43
Q

Describe the ordovician?

A

Second largest mass extinction - 85% of species and half of all marine species disappeared.

2015 - new evidence implicates changes in ocean chem associated with decrease in oxygen that caused an increase in dissolved metals.

44
Q

What is phyletic gradualism?

A

Darwin -
Adaptations are result of slow gradual process where beneficial variant slowly increases in frequency - eventually leads to formation of new species ie. equine evolution.

New species arise from gradual transformation of ancestral species through slow, constant change

45
Q

What is punctuated equilibrium?

A

Eldredge and Gould - Major evolutionary change occurs in rapid bursts of morphological and phylogenetic changes followed by periods of stasis (absence of change). ie. Cambrian explosion (543-490 mya) - spike in marine genera and species. Evidence from Burgess Shale in BC.

46
Q

Does punctuated equilibrium contradict Darwin?

A

No, it just suggests additional mechanism for evolutionary bursts.

BIOL 2600 (6 decks)

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