Download Daphnia pulex

Background genetic and electrophoresis data on Daphnia pulex (SS) and D.
pulicaria (FF), the parental species for the Round Lake population.
Crosses
Potential offspring
(f) SS X (m) FF
SF (diploids)
SF (diploids)
Geographic location
of Daphnia sp.
Temperate zone
populations
Reference
Crease et al., (1989)
Colbourne et al., (1998)
(f) CP SS X (m) OP SF
SS (CP) SF (CP)
Illinois, US
Larsson, P. (1991)
SS (OP)* SF (OP)
(f) CP SF X (m) OP SF
SS (CP) SF (CP)
Illinois, Iowa,
Heier & Dudycha, (2009)
SS (OP) SF (OP)
Michigan & Oregon
◊ FF outcome not
Windsor, ON;
Xu et al., (2013)
mentioned
Michigan, US
(f) CP SS X (m) OP SS
SS (CP)
Windsor, ON;
Xu et al., (2013)
SS (OP)
Michigan, US
(f) CP SF X (m) OP SS
SS (CP) SF (OP)
SS (OP) SF (CP)?
(f) females; (m) males; CP cyclic parthenogens; OP obligate parthenogens.
SS slow slow, SF slow fast, and FF fast fast; electrophoresis scores for lactate dehydrogenase
allozymes.
* Not present in their lab results.
Preliminary electrophoresis for Round Lake
Fall/Winter 2011: Random adult selection of pale and Hb rich phenotypes
Results of 177 tested
155 Ldh test (SS)
20 Ldh test (SF); 2 were pales
88.6 % (SS)
11.4 % (SF)
Diagnostic electrophoresis test for lactate dehydrogenase allozymes was used to determine which
species we have in Round Lake (Hebert & Beaton, 1993; Crease et al., 2011). Daphnia pulex (Ldh SS) and
D. pulicaria (Ldh FF) crosses result in D. pulex hybrids (Ldh SF). D. pulex (Ldh SS) individuals may also be
hybrids for reasons that will be addressed below.
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Microsatellite work by Cristecu et al. (2012), in D. pulex and D. pulicaria Fst= .43 to .52 ; means a
clear genetic divergence in the nuclear genome
Daphnia pulex complex may be either cyclic parthenogens (CP) (males are not always produced),
or, obligate parthenogens (OP) that carry meiosis suppression (may or may not produce males).
D. pulicaria are cyclic parthenogens, i.e. females can reproduce sexually, (males are not always
produced) (Xu et al., 2013).
Xu et al. (2013) NJ tree (neighbour-joining tree, microsatellite) 3 distinct clades; D. pulex “pure”
(let’s call it clade A; this has the more anciently introgressed diagnostic alleles from D. pulicaria,
most are CP but some OP SS), D. pulex hybrids (clade B; they are all OP SF or OP SS), and D.
pulicaria (clade C; they are all CP FF)
The hybrid index for clade A is H=0 which means the D. pulex SS (OP) individuals have almost NO
D. pulicaria genes; the SF (OP),clade B, on average have an H=0.29, F1 generation hybrid
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simulation H=0.5 or you take SF1 X SS (CP) simulation H=0.25; two individual SF (OP) had H=0
suggesting they are individuals from a “more advanced backcross” (Xu et al., 2013).
Obligate parthenogenesis probably originated from hybridization, backcrosses, and
introgression of alleles from D. pulicaria because the meiosis suppression/OP comes from D.
pulicaria diagnostic alleles (Xu et al., 2013) but, also from D. pulex OP individuals that carry an
allele ”containing an identical upstream insertion of a transposable element as well as a
frameshift mutation” which plays a role in meiotic cohesion (Eads et al., 2012)
all obligately asexual clones carry an allele on the following gene linkage groups V, VIII, IX, & X
(Lynch et al., 2008) and gene linkage group I (Xu et al., 2013) these groups play some kind of role
in meiosis suppression, (ie. they suggest, activation of unfertilized diploid resting eggs or
transmission of OP)
Another point of importance to Round Lake population study; for SS individuals and SF
individuals, the Ldh test “cannot be reliably used to distinguish between hybrids and
nonhybrids” because Xu et al., (2013) found some individual SF (OP) types that are as far
removed (genetically) from D. pulicaria as were some of the SS (OP) individuals
Paland & Lynch (2006) in their excess amino acid substitution study (asexual versus sexual D.
pulex), state that early phases of an invading asexual line may outcompete sexual lines but over
time “sexual reproduction enhances the efficiency of purifying selection”. Their results support
the conclusion that an accumulation of deleterious mutations will occur in asexuals and lead to a
reduction in their longevity.
References cited:
Colbourne JK, Crease TJ, Weider LJ, Hebert PDN, Dufresne F, Hobaek A (1998) Phylogenetics and
evolution of a circurmarctic species complex (Cladocera: Daphnia pulex) Biological J of the Linnean
Society 65: 347-365.
Crease TJ, Floyd R, Cristuescu ME, Innes D (2011) Evolutionary factors affecting Lactate dehydrogenase
A and B variation in the Daphnia pulex species complex. BMC Evolutionary Biology 11: 212.
Crease TJ, Stanton DJ, Hebert PDN (1989) Polyphyletic origins of asexuality in Daphnia pulex. 11.
Mitochondrial-DNA variation. Evolution 43: 1016-1026.
Cristescu, ME, Constantin A, Bock DG, Cáceres CE, Crease TJ (2012) Speciation with gene flow and the
genetics of habitat. Molecular Ecology. 21, 1411-1422.
Eads BD, Tsuchiya D, Andrews J, Lynch M, Zolan ME (2012) The spread of a transposon insertion in Rec8
is associated with obligate asexuality in Daphnia. Proceedings of the National Academy of Sciences, USA,
109, 858–863.
Hebert PDN, Beaton MJ (1993) Methodologies for Allozyme Analysis using cellulose acetate
electrophoresis. A Practical handbook, Helena laboratories 1-34.
Heier CR, Dudycha JL (2009) Ecological speciation in a cyclic parthenogen: sexual capability of
experimental hybrids between Daphnia pulex and Daphnia pulicaria. Limnology and Oceanography, 54,
492–502.
Larsson P (1991) Intraspecific variability in response to stimuli for male and ephippia formation in
Daphnia pulex. Hydrobiologia 225: 281-290.
Lynch M, Seyfert A, Eads B, Williams E (2008) Localization of the genetic determinants of meiosis
suppression in Daphnia pulex. Genetics, 180, 317–327.
Paland S, Lynch M (2006) Transitions to asexuality result in excess amino acid substitiutions. Science,
311.
Xu S, Innes DJ, Lynch M, Cristescu ME (2013) The role of hybridization in the origin and spread of
asexuality in Daphnia. Molecular Ecology (2013) 22, 4549–4561