Week 8 Flashcards

Question

What is an example of geographical hybridisation in non-ring species?

Answer 1

Spotted Towhee (Pipilo maculatus) and Collared Towhee (P. ocai) Hybridise some areas where they co-occur but not in others

Answer 2

Uses increasing phylogenetic data Seperateness in a phylogeny reflects genetic isolation Widely application, can be used for asexual and extinct organisms

Answer 3

Robst phylogeny not always avaliable. especially phylogeny Not clear what characters should be used to contrust phylogeny Doesnt lead to stable systematics, since phylogenies change as new data emerge

Answer 4

Forest Elephant (Loxodonta cyclotis) v. Savannah Elephant (L. africana): Forest Elephant is smaller (2.5m high v. 3-4m high) and has straighter, thinner tusks, rounder ears and differently-shaped skull Phylogeny based on 4 nuclear genes Forest v. Savannah Elephants show 58% of difference shown between African and Asian Elephants

Answer 5

Combines elements of previous definitions Operational definition, aims to seperate definition of species from hypotheseses about how speciation occurs Does not assume complete reproductive isolation is required to define a species

Answer 6

Element of subjectivity remains Not widely used

Answer 7

Heliconius cydno and Heliconius melpomene crossed in laboratory to re-create Heliconius heurippa H. heurippa: Occurs in nature (in Colombia) Does not breed with putative parent species Hybrid genome

Answer 8

Under MSC, Red Wolf is a species Under BSC, it is not a species as it hybridises with the Coyote Phylogenetic SC - suggests red wolves result from hybrids between the Gray Wolf and the Coyote!

Answer 9

Fruitfly Drosophila pseudoobscura 4 reared on starch-based medium and 4 reared on maltose-based medium 2 groups became differentially adapted to media 1 year after start, mating experiments performed

Answer 10

Positive assortative mating: individuals from each group prefer to mate with opposite sex from same group, even across cages Reproductive isolation as a by-product of adaptation to media (not separation per se).

Answer 11

Polychaete worm Nereis acuminata Lab population founded in 1964 from 5-6 individuals, grew to 1000s, 4 pairs selected in 1986, new population grew to 1000s (two ‘bottlenecks’) Test against field populations for pre-mating and post-mating isolation

Answer 12

Pre-mating: In Lab-Field crosses, worms more reluctant to mate than in Lab-Lab or Field-Field crosses Post-mating: In Lab-Field crosses, 0% offspring survived; in Lab-Lab or Field-Field crosses, 75-95% offspring survived Reproductive isolation (with hybrid sterility) as a by-product of bottlenecking and/or adaptation to lab environment

Answer 13

Any intrinsic process or phenomenon that forms a barrier to gene flow between populations but excludes (large-scale) physical separation per se

Answer 14

Premating barriers: by-products or products of selection for avoidance of hybridisation (reinforcement), if populations have hybridised in the past and hybrids have reduced fitness Postmating barriers: by-products, since, for example, cannot be selection for greater degree of sterility in hybrids

Answer 15

Bishop Pine (Pinus muricata) v. Monterey Pine (P. radiata) in California: former sheds pollen late in year, latter early in year, so do not cross although can be made to hybridise

Answer 16

Dixie Iris (Iris hexagona) v. Copper Iris (Iris fulva) in SE USA: hybridise where habitats meet in Louisiana

Answer 17

Field Grasshopper (Chorthippus brunneus) and relatives (C. biguttulus and C. mollis) look very similar but have different male songs: interspecific matings occur if ‘right’ song is played in laboratory; plus Fireflies: females respond only to male flash pattern of their own species

Answer 18

Congeneric monkeyflowers (Mimulus lewisii and M. cardinalis) differ in floral form and hence in pollinators (bees v. hummingbirds)

Answer 19

Damselflies, males clasp females across the thorax; female inserts tip of abdomen into underside of midbody of male to pick up spermatophore that male has placed there; there is fine match of these structures – any mismatch makes the copulation unsuccessful

Answer 20

Sea-urchins and abalones, only conspecific fertilisation occurs because biochemical compatibility gametes required in abalone, there is a species-specific relationship between lysine in sperm head and vitelline envelope surrounding egg)

Answer 21

Allopatric taxa - increase in genetic difference means greater prezygotic isolation Sympatric taxa - small genetic difference can mean total prezygotic isolation

Answer 22

Hybrid inviability: hybrid embryos die during development, e.g. Wood Frog (Rana sylvatica) x Leopard Frog (R. pipiens)

Answer 23

Hybrid sterility: e.g. a mule is a (viable) hybrid between Horse (Equus caballus) and Donkey (E. asinus) but is sterile owing to unequal chromosome numbers (Horse: 2n = 64; Donkey: 2n = 62)

Answer 24

Cytotypes of grasshopper Caledia captiva in Australia: in hybrid zone, F1 hybrids are common but F2 hybrids are rare (because die during embryonic development)

Answer 25

Fitness of F2 hybrids of African haplochromine cichlid fish bred from species pairs spanning several thousand to several million years divergence time. F2 hybrids consistently showed the lowest viability compared to F1 hybrids and non-hybrid crosses

Answer 26

Hybridisation of Heliconius melpomene and H.cydno Hybrids are attacked by birds at a much higher rate then either of the parent species

Answer 27

Rhagoletic pomonella Invest hawthorn vs apple, 150 years ago Differ in six allozyme loci

Answer 28

Pre - host plant fidelity and allochronic isolation (apples ripen earlier) Post - no intrinsic inviability/sterility of hybrids expect ecological isolation from host-specific adaptation

Answer 29

Hawthron is better food for both races Apples do have less interspecific competition, less parasites and lower population density Fitness maybe similar but not enough to cuase isolation

Answer 30

Hawthron race developes fast and Apple race is slow Pupae overwinter but diapause is faculative Apples avaiable 3 weeks earlier and apple race pupates 16 days earlier Fast development on apples - breaks diapause before winter dies Slow development on hawthorn - not ready to enter diapause by winter Hybrid impactes development speed so either too fast or slow

Answer 31

Region where genetically distinct populations meet and mate, resulting in at least some offspring of mixed ancestry

Answer 32

Population genetic differentiation correlated with environmental discontinuities (with hybrid zones along these discontinuities)

Answer 33

Two formerly separate populations expand, meet and interbreed, but do not necessarily merge

Answer 34

Yellow-bellied Toad (Bombina variegata) of western Europe, Fire-bellied Toad (B. bombina) of eastern Europe Ranges contact in narrow (6km wide ) hybrid zone in central Europe Hybrids have lower rates of survival (= postzygotic isolating barrier) Ancestors confined to refuges in southern Europe in Pleistocene glacial period Secondary contact on spread from refuges in SW and SE Europe, respectively

Answer 35

Balance of dispersal and degree of hybridisation - bringing about gene flow - and selection against hybrids - preventing gene flow

Answer 36

Two populations fixed at a locus for alleles A and a (hence populations are AA and aa) Dispersal of AA individual into aa range, followed by mating, creates Aa hybrid; mating of this F1 hybrid with aa individual introduces A into aa population (introgression) But if Aa hybrids are less fit (postzygotic isolating mechanism), then introgression does not occur or occurs rarely Hence steepness of cline determined by balance of amount of gene flow and strength of selection against hybrids

Answer 37

Lower than parental fitness have a relatively narrow and short lived hybrid zone and increase in reinforcement of parental populations Equal to parental fitness have a relatively wide and long lived hybrid zone and parental populations coalesce Higher than parental fitness depends on fitness advantage occurs in ecotone or new habitat ends with stable hybrid zone or formation of a new species

Answer 38

Allopatric speciation (geographically separated populations become reproductively isolated) Parapatric speciation (geographically neighbouring populations become reproductively isolated) Sympatric speciation (geographically overlapping populations become reproductively isolated)

Answer 39

Vicariance (an existing population is subdivided into one or more smaller populations) Peripatric speciation (a larger parental population gives rise to a smaller population at its periphery, by subdivision or by dispersal)

Answer 40

Land bridges Glaciation Mountain formation Continental drift Climatic change Barrier prevents (or severely reduces) gene flow. Most common mode of speciation in animals

Answer 41

Current Isthmus closed 3 million years ago – developing long before that. Different sides of the Isthmus experience different environmental conditions – salinity, clarity, temperature, tidal fluctuations. Upwelling-driven, plankton-based ecosystem on the Paciﬁc side and a coral-reef-based, clear-water ecosystem in the Caribbean Lots of taxa are different on each side of the Isthmus.

Answer 42

16 taxa (eight putative geminate species pairs) within the genus Alpheus. Strong reproductive isolation between species pairs in Lab 1% of interspecific matings yield fertile offspring vs 60% of conspecific Molecular clocks indicate species pairs did not all diverge at the same time – range of dates from 3mya to 10mya

Answer 43

Reproductive compatibility is correlated with genetic distance, low reproductive compatibility is correlatied with genetic divergence

Answer 44

Same mechanism as allopatric speciation except that the isolated population is very small (1 to 100 individuals). May involve invasion of new habitats Genetic drift becomes important in small populations.

Answer 45

Founder events Isolation of peripheral population. Non-peripheral population could become isolated from rest (rare?).

Answer 46

Reproductive isolation evolves between two populations that are exchanging some genes. “Clinal models” involve a single species distributed across a variable environment. Subpopulations become adapted to their local environments “Stepping stone” models involve discrete populations having limited genetic exchange.

Answer 47

New species form within a freely interbreeding population “the origin of an isolating mechanism (i.e. a barrier to gene flow) among the members of an interbreeding population” Should evolve within the average dispersal distance of a single individual Not caused by geography or distance but be some biological feature of organisms Remains controversial and is probably quite rare if it does occur

Answer 48

1- The species must be largely or completely sympatric. Although presently allopatric species may have arisen in sympatry, this will usually be impossible to determine. 2- The species must have substantial reproductive isolation, preferably based on genetic differences. 3- The sympatric taxa must be sister groups. The genetic similarity used to establish this fact must not result from hybridisation. 4- The biogeographic and evolutionary history of the groups must make the existence of an allopatric phase very unlikely.

Answer 49

Cichlid fish Small conical lakes that are isolated 11 spp in lake Barombi Mbo and 9 spp in lake Bermin, all species are endemic Species differ in diet feeding morphology and breeding colouration No hybrids found

Answer 50

The “monophyly” (descent from a common ancestor) of the two radiations shown above is weaker than previously thought. The authors conclude that this monophyly, which is crucial evidence for sympatric speciation, is not strongly supported

Answer 51

Substantial introgression (movement of genes) between not only some of the species in each of the two radiations, but also between the species in the lake and different “outgroup” species in rivers outside the lakes. This suggests that there have been multiple invasions of the lakes by ancestors of the crater-lake fish, and this again militates against a single common ancestor forming multiple species in the lake

Answer 52

The native flora of LHI comprises 242 species in 179 genera. In 139 genera only a single species is present on LHI; of these species, 42 are endemic to the island The remaining 40 genera include between two and six LHI species. In 13 cases, all species are endemic; in 15, all are non-endemic; and the remaining 12 genera contain a mixture of endemic and non-endemic species

Answer 53

When modeled 55.4% of trees arrived by colonisation 24.8% of cases by Allopatric speciation Sympatric speciation depending on strength of cases was either 3.7% or 4.5%