Sex Determination and Genome Size in Catolaccus grandis (Burks, 1954) (Hymenoptera: Pteromalidae)

2008·4.4 MB·

by  N M Barcenas

HYM. RES.
J.
Vol. 17(2), 2008, pp. 201-209
Sex Determination and Genome Size in Catolaccus grandis (Burks, 1954)
(Hymenoptera: Pteromalidae)
N. M. Barcenas, N. Thompson, V. Gomez-Tovar, A. Morales-Ramos and
J. J.
J. S. Johnston
(NMB) Heritage University, 3240 Fort Rd, Toppenish, WA 98948, USA
(NJT) Department of Biology, Texas A&M University 3258, College Station, TX 77883, USA
(VGT) SENASICA-SAGARPA Insurgentes Sur 498, 06100 Mexico, D.F.
(JAMR) USDA-ARS National Biological Control Laboratory, Biological Control of Pests Research
Unit 59 Lee Road Stoneville, MS 38776, USA
(JSJ) Department of Entomology, Texas A&M University 2475, College Station, TX 77883, USA
—
Abstract. Complementary sex determination (CSD) is a common form of the haplodiploid sex
determination system found in all wasps, ants, andbees (Hymenoptera). Exceptions exist to CSD,
buttoo fewhavebeen documented to make phylogenetic conclusions. Males thatare homozygous
at CSD loci are diploid and often sterile. Any effect that increases homozygosity (inbreeding and
small population size) should increase the proportion of diploid males. We use flow cytometry to
determine the genome size of males and females of the parasitic wasp Catolaccus grandis (Burks)
(Hymenoptera: Pteromalidae) (1 C = 455.4 ± 3.4 mb). We then score haploid and diploid males
(and females) frompopulations thatwere 25% and50% inbred. None ofthe 314males scoredwere
diploid. We conclude that the CSD system is very unlikely to exist in this species and discuss the
implications for sex determination systems in the Pteromalidae and other chalcidoids.
Evolving independently at least eight haploids that have one CSD allele. Unipa-
and possibly as many as 15 times in mites rental males are typically produced as
and insects (White 1973, Mable and Otto unfertilized eggs, but in some cases are
1998) in phylogenic lineages that represent produced as zygotes inwhich one parental
nearly 20% of all animal species (Bell 1982, genome is excluded post fertilization (Kel-
Bull 1983), haplodiploidy is the sole repro- ler et al. 2001, Beukeboom et al. 2007).
ductive mode in Hymenoptera, including The CSD form of arrhenotoky fails when
the pteromalid wasp Catolaccus grandis the female is fertilized by a male whose
(Burks, 1954) (Hymenoptera: Pteromali- single allele at the CSD locus is identical to
dae) studied here. The most common one of the two CSD alleles that she carries.
system of haplodiploidy is arrhenotokous V/hen this happens, half of her diploid
reproduction, where females develop from fertilized progeny (all of whom should
fertilized eggs and males from unfertilized develop as female) are homozygous for a
eggs. The most studied form of arrhenot- CSD allele and develop into biparental
oky is the complementary sex determina- diploid males. Diploid males were first
tion (CSD) mechanism, whereby a sex observed in a single locus CSD (sl-CSD)
locus with multiple alleles determines the system by WTiiting in Bracon hebetor Say,
sexual development ofthe offspring (Whit- 1836 (Whiting 1943) but have been ob-
ing 1943, Beye et al. 2003). In the CSD served invery many species since (Trent et
system, zygotes heterozygous at the CSD al. 2006). Diploid males are often sterile,
locus develop into biparental diploid fe- yet lacking the division of chromosomes
males; males are produced as uniparental required to produce haploid sperm, may
202 JournalofHymenoptera Research
produce diploid sperm and consequently, population bottlenecks, and inbreeding
sterile triploid females (Whiting 1943, leading to a loss of the sex alleles.
Stouthamer et al. 1992, Cowan and Stahl- Economically important hymenopterans
hut 2004). Whether in natural populations are among the best studied, and their sex
or in laboratory reared colonies, diploid determination is amongthebest document-
males and triploid sterile females represent ed. Thesl-CSDsystemiswelldemonstrated
a reproductive cost, affecting fertility and in the red imported fire ant (Solenopsis
Wu
sex ratio (Stouthamer et al. 1992, et al. invicta Buren, 1972) and the honeybee Apis
2005, see exception in Cowan and Stahlhut melliferaL., 1758 (Hymenoptera: Apidae); 11
2004). Production of diploid males and to 19 alleles were determined for the
triploid females is most apparentwhen the complementary sex determiner (csd) locus
number of CSD alleles is reduced by in honey bees (Beye et al. 2003), with a
population bottlenecks and founder smaller number of alleles (8 to 13) in the
events, or when homozygosity increases population of red imported fire ants, that
as a result of consanguinity. The latter is wentthroughabottleneckwhenintroduced
important, since inbreeding by sib-mating into southern United States (Ross et al.
occurs often in hymenopteran species that 1993). The occurrence of CSD in the
are solitary or are social parasites Hymenoptera has been demonstrated in
(Schrempf et al. 2006). symphytan, ichneumonid, and braconid
The parasitoid pteromalid wasp, C. species, but to date not in chalcidoids
grandis, is economically important for use (Stouthamer et al. 1992). In several of these
in bio-control of the boll weevil, Anthono- groups apparent exceptions exist, specifi-
mous grandis (Boheman, 1843) (Coleoptera: callyin instances where inbreedinghas not
Curculionidae), and has been released exposed sl-CSD (Wu et al. 2005).
experimentally for crop management in The relative phylogenetic position of
many areas of the southern U.S.A., includ- pteromalids withinthe tree oflife is largely
ing the Rio Grande Valley, Texas, San unknown, although studies are underway
Angelo, Texas, and Aliceville, Alabama to remedy this situation (Castro and
(Morales-Ramos et al. 1994, 1995a, 1998, Dowton 2005, J. Heraty personal commu-
Summy et al. 1995, 1997). An ectoparasi- nication). Understanding the kind of sex
toid, C. grandis lays its eggs on boll weevil determination system and the ancestral or
larvae (mostoftenthe third instar orpupa), derived state of the CSD system should be
greatlysuppressingthenumbers oftheboll part of this phylogenetic effort. We assume
weevil and thereby reducing the damage that CSD is the ancestral mode of repro-
caused to cotton (Summyetal. 1995). As an duction. There is little published research
idiobiont, the female stops host develop- to prove this, however, especially in the
ment with a paralytic venom (Morales- more ancestral taxa (Cook and Crozier
Ramos et al. 1995b) and the emerging larva 1995). Here we test the hypothesis that a
consumes its paralyzed host. These char- form ofthe CSD system exists in C. grandis.
acteristics may give an advantage as an This represents the second test of CSD in
efficient biocontrol agent (Morales-Ramos Pteromalidae. We employ a new approach
etal. 1995b). However, production efficien- in studying CSD by determining genome
cy in insect mass rearing of C. grandis and size first, and then directly scoringmales of
related species can be problematic if sl- consanguineous matings, using flow cy-
CSD is present, because that would neces- tometry to score ploidy level. If a CSD
sitate a large number of sex alleles to system exists in this species, diploid male
minimize diploid male production. Special production, to the extent they survive, will
measureswould need tobe takenincolony be directly proportional to the level of
management to avoid founder events, consanguinity.
Volume 17, Number2, 2008 203
METHODS genome size and ploidy level following
Johnston et al. (2004). The head and thorax
Live Material
of a C. grandis was placed in a 1.5 ml
Catolaccus grandis from wild-caught in- Kontes Dounce tissue grinder into 1 ml of
dividuals were used to initiate a reared cold Galbraith buffer (per litre: 4.26 g
population. The lab colony used here was MgCl2, 8.84 g sodium citrate, 4.2 g 3-[N-
foundedwith: 6 genomesfromElSalvador, morpholino] propane sulfonic acid, 1 mL
Central America (host plant ofboll weevil: Triton X-100, 20 Hg/mL boiled Ribonucle-
wild and cultivated cotton), 56 genomes ase A, pH 7.2; Galbraith et al. 1983).
from Tabasco, Mexico (host plant of boll Chicken red blood cells (CRBCs) were
weevil: Hampea nutricia Fryxell (Malva- added to act as standards (1 C =
ceae)), and 15 genomes from Oaxaca, 1212 Mb; Bennett et al. 2003). To release
Mexico (host plant of boll weevil: Cienfue- and isolate nuclei, the head and thorax
gosia rosei Fryxell (Malvaceae)). All C. plus the CRBCs in buffer solution were
grandis in this study were from controlled stroked 15 times with an A pestle and
matings among reared individuals. filtered through a 20-|im nylon filter.
Propidiumiodide, anintercalatingdye that
Crosses binds stoichiometrically to DNA and fluo-
—
A. Sib-matingoffspring. Virgin C. grandis resces indirectproportiontothe amountof
females were mated with a single male. DNA present, was added to a final
Their offspring were confined in individu- concentration of 50 ppm, and the mixture
al Petri dishes and allowed to mate (sibling co-stained in the dark at 4°C for 20-
matings). Each female was isolated in a 40 minutes. The mean fluorescence of co-
Petri dish 3-4 days after emergence for stained nuclei in replicate samples of each
independent offspring evaluation. Host sex was quantified using a Coulter Epics
boll weevil larvae were presented to the Elite (Coulter Electronics, Hialeah, FL)
C. grandis females encapsulated in Para- with a laser tuned at 514 nm and
film® using the method described by Cate 300 mW. Individual nuclei separate and
(1987). Twelve Parafilm® encapsulated boll pass across the exciting light source in the
weevil larvae per female per day over five flow cell ofthe cytometry, where the nuclei
days were provided as hosts. Females that are counted and the fluorescent light
produced only male offspring were dis- emitted from each nuclei is collected and
carded (presumably they were not fertil- quantified after passing a longpass filter to
ized and had no opportunity to produce eliminate anyreflected laserlight. To avoid
diploid males). Male offspring of fertilized counting debris or nuclei with associated
females were prepared for flow cytometry. cytoplasmic tags, counting was activated
—
B. Backcross offspring. Virginsiblingcou- by PI fluorescence, and only clean, singlet
pleswereisolatedinPetridishes, allowedto nuclei with low light scatter were included
mate, and were removed after offspring in the analysis. Genome size was estimated
emergence. Families with only male off- for each male and female C. grandis by first
spring or without father survival were calculating the ratio of the fluorescent
discarded. Daughterswerepairedwiththeir intensity of C. grandis nuclei to that of the
fathers to induce mating and allowed to CRBCs standard. The genome size was
reproduce. Again,offspringwithonlymales then determined by multiplying this ratio
were not included in the analysis. by the amount of DNA in the CRBCs.
Flow Cytometry Analysis
Individual C. grandis males were pre- The genome size of C. grandis is given as
pared for flow cytometric analysis of the average (+/— standard error) of the
204 Journalof Hymenoptera Research
estimated genomes. A minimal estimate of needed to detect diploid males (Table 1).
the likelihood of scoring a diploid male is All males produced from the backcrosses
based on a binomial distribution, where (190 in total) were haploid.
theexpectationofa diploid male is equalto If the CSD system exists for C. grandis,
the probability ofhomozygosity, assuming inbreeding should increase homozygosity
sufficient numbers of alleles at indepen- and result in significant diploid male
dent CSD loci that inbreeding is the only production. Given haplodiploid sex deter-
source of homozygosity. mination, sib mated and backcross zygotes
had a probability of homozygosity at a
RESULTS AND DISCUSSION
single locus of 0.25 and 0.50 respectively.
The genome size of C. grandis was The failure to observe diploid males
estimated using a chicken red blood cell among the 314 scored males indicates that
(CRBC) (1 C = 1212 Mb) standard and a CSD system, if it occurs at all in C.
measured 1 C = 455.4 ± 3.4 Mb (Fig. 1 A, grandis, involves >5 independent loci. The
B). As expected, the haploid genome of probability that diploid males will be
males was half that of the diploid genome produced in significant numbers due to
of females. The C. grandis genome is 1.37 sib mating in nature, or due to small
times larger than that of the only other effective size in mass rearing colonies is
pteromalid genome scored to date, N. low.
uitripennis (Walker) (1 C = 332.5) and 3 A possible source of error in these
times larger than the genome of the only analyses is cannibalism or other forms of
scored braconid wasp, Habrobracon juglan- reduced survival of diploid males. Selec-
dis (Ashmead, 1889) (1 C = 156.5) (Raschet tive cannibalism based on semiochemicals
al.1975). is known to occurinhoneybees, where the
Catolaccus grandis were easily scored for workers will consume any diploid males
ploidy level. Females revealed only a (Woyke 1963). A parasitoid of the codling
diploid peak (Figure 1A). Haploid males moth, Liotryphon caudatus (Ratzeburg, 1848)
showed 2 fluorescent peaks with equal (Hymenoptera: Ichneumonidae) with
numbers of haploid and diploid (endo- known cannibalism produces a significant
reduplicated) nuclei (Fig. 1 B). This endo- diploid male population (T. R. Unruh,
reduplicated peak is observed because of personal communication). This suggests,
the diploid tissue found in the muscle that in some haplodiploid species, canni-
(Johnston et al. 2004). Diploid males (if balism does not necessarily lead to selec-
present) would have shown only one tive killing of diploid males. In culture, C.
strong diploid peak, as observed in the grandis females lay eggs either on the boll
females. All 124 males from the F-2 gave a weevil larvae or on the interior surface of
strong haploid peak as seen in Figure 2; no the Parafilm® capsule where the host is
diploid males were scored. These results presented as Parafilm® encapsulated lar-
indicate that a CSD system, if it exists, is vae. In the rearing conditions here, the
based on a number of loci in a multilocus female is expected to lay 1, 2, or 3 eggs per
complementary sex determination system host. An emerged C. grandis larva will
(ml-CSD). A second setofinbredbackcross move around and eat any other eggs or
offspring was produced, collected, and larvae that it encounters (Morales-Ramos
scored in order to estimate more precisely and Cate 1992), and rarely are two para-
thenumberofgenesinvolved inapotential sitoid pupae found in the same host.
ml-CSD system. Backcross offspring were Two sources of data suggest that diploid
selected because the expected 50% homo- male mortality cannot explain the absence
zygosity in the backcross to the haploid of diploid males in our study. Fully 44.4%
male parent reduces the sample size of hosts receive a single egg, and the
Volume 17, Number2, 2008 205
A
62
46 Female 2C
31
CRBC2C
15
Female4C
u
3
C
-I —-i
Relative Fluorescence (channel number)
Fig. 1. RelativeDNAstaininginnucleifromthehead ofA) femaleCatolaccusgrandispluschickenredblood
cells (CRBCs)andB)haploidmaleC.grandisplusCRBCs. Neuraltissueproducesthefirst1 Cpeakinhaploid
males.DNAinthenucleiofmuscleislargelyendoreduplicatedinhaploidmales(Johnstonetah,2004)resulting
inthediagnostic1C,2Candsmall4Cpeaksshownhere.RelativeDNAamountiscalculatedastheproductof
theratioofthemeanfluorescenceoftheleftmostpeak(1 Cinhaploidmales,2 Cinfemales)/meanfluorescence
ofCRBCstandardmultipliedbytheestimatedgenomesizeoftheCRBCstandard(1140Mb;Bennettetal.2003).
206 Journalof Hymenoptera Research
50
45 p.
y/) 40
A3 Haploid (1C) Males
=3 I
"O 35
>
30
TJ
C
25
MO— Diploid (1C) Females
i_ 20
(U \
-Q 15
£
10
5
J-fl^ MM
ffl Pi Pi
I i i
39 78 117 156 196 235 274 313 352 391 430 469 509 548
Genome Size (Mb)
Fig. 2. Relative genome sizes ofindividuals ofhaploidmales and diploid females.
remainder (55.6%) receive two or more (Morales-Ramos and Cate 1992). A reduc-
eggs (Fig. 3). Even under the assumption tion in sex ratio (more surviving males)
that diploid males from single egg hosts (1.2:1) was observed inthebackcrosses,but
are the only ones that survive cannibalism, this could be related to the age of the
a significant number of diploid males in a father. Gomez etal. (1997) exposed avirgin
CSD system would be expected. Addition- female every day during the life span of C.
al evidence that diploid males should have grandis males and observed a reduction
survived cannibalism is supported by the over time in the ability of males to
observation that there was no deviation of inseminate females.
the sex ratio from what was expected. Inbreeding, because it increases the
Under lab conditions, the sex ratio ob- chance ofhomozygosityand thus increases
served for the sib-matings was approxi- the appearance of diploid males, reduces
mately 2.8:1. The previously published sex the fitness of species with sl-CSD. In
ratio in natural populations is 3:1 or 4:1 species with proven CSD, the effect of
populationbottlenecks and founder events
Table 1. Sample size needed to detect a diploid that decrease the number of alleles and
male in F2 and backcross offspring (BC), given a sex increase inbreeding may be reduced by
determining system with one to five genes involved modification of the CSD system, including
(ml-CSD) anda4:1 female: malesexratioinfertilized inbreeding avoidance behaviors, and the
females under random mating based on binomial
development of a non-CSD system (Cook
distribution.
and Crozier 1995, Dobson and Tanouye
F2 BC 1998). One modification of CSD is to
Numberofloci P=95% P=99% P=95% P=99% involve multiple loci, although the sex
determination mechanism remains the
1 10 13 4 6
2 18 27 6 9 same: females are heterozygous at one or
3 66 101 10 15 more loci, while full fertility is expected
4 258 396 18 27 only in haploid males where each CSD
5 1025 1575 35 76
allele is present as a single copy (Paxton et
Volume 17, Number2, 2008 207
350
en
"D 300
O
250
A3
TO 200
Q_
O 150
J—
-Q 100
£
D
50
z:
2 3 4 >5
Number of eggs per host
Fig. 3. Thenumberandpercentage (inparenthesis) of721 hostsparasitizedby 1,2, 3,4and 5 ormoreeggs.
al. 2000). In ml-CSD, the chance of a tera: Braconidae) (Wu et al. 2005). It is also
homozygous diploid male is greatly re- absent in the more distantly related ant
duced, even in inbreeding populations. Cardiocondyla obscurior Wheeler, 1929 (For-
Inbreeding effects have not been well micidae), which shows no evidence of
tested experimentally for many Hymenop- diploid males but does show inbreeding
tera, however, and it can be argued that depression (Schrempf et al. 2006). Pro-
ml-CSD has notbeen persuasively demon- posed alternative sex determination mech-
strated (Beukeboometal. 2007), leavingthe anisms in arrhenotokous insects include
as best-known mechanism for inbreeding genomic imprinting, fertilization sex deter-
avoidance in the presence of CSD, the mination, genie balance sex determination,
premating dispersal observed in Bracon and maternal effect sex determination,
hebetor (Ode et al. 1995). Because we which were all tested in populations of N.
experimentally controlled matings, mecha- vitripennis (Dobson and Tanouye 1998,
nisms to avoid inbreeding were not an Beukeboom et al. 2007). The genomic
issue, and even an ml-CSD system is imprintingmodel fitswell forN. vitripennis
unlikely. (Trent et al. 2006) and may also be present
Single locus CSD hasbeen demonstrated in related Chalcidoidea.
for at least 60 species of hymenopterans Flow cytometry allowed us to quickly
(Beukeboom et al. 2007), including most score for diploid male production, and we
social species that have been studied (see showed that the CSD model is unlikely to
exception in Schrempf et al. 2006). How- be the sex determination mechanism for
ever, the CSD system is not the only the pteromalid, C. grandis. These results,
mechanism for arrhenotokous reproduc- along with fairly compelling evidence to
tion. The absence of sl-CSD system has reject CSD in one Trichogrammatidae
been conclusively demonstrated in Nasonia (Chalcidoidea) species (Stouthamer and
vitripennis (Walker, 1836) (Hymenoptera: Kazmer 1994), raise the question ofwheth-
Chalcidoidea) and the parasitoid Hetero- er the CSD model arose independently or
spilus prosopidis Viereck, 1910 (Hymenop- in a common ancestor of these species.
208 Journalof Hymenoptera Research
LITERATURE CITED Johnston,J. S.,L. D. Ross,D. P. Hughes,L.Beam,and
J. Kathirithamby. 2004. Tiny genomes and endo-
Bell, G. 1982. The Masterpiece ofNature: The Evolution reduplication in Strepsiptera. Insect Molecular
and Genetics ofSexuality. University of California Biology 13: 581-5.
Press, Los Angeles. Keller, L., C. Liautard, M. Reuter, W. D. Brown, L.
Bennett, M. D., I. J. Leitch, H. J. Price, and J. S. Sundstrom,andM.Chapuisat.2001.Sexratioand
Johnston. 2003. Comparisons with Caenorhabditis Wolbachia infection in the ant Formica exsecta.
(-100 Mb) and Drosophila (-175 Mb) usingflow Heredity87: 227-233.
cytometry show genome size inArabidopsis tobe Mable,B. K. andS. P. Otto. 1998. Theevolutionoflife
-157Mb and thus -25% larger than the Arabi- cycleswithhaploidanddiploidphases.BioEssays
dopsis initiative estimate of —125 Mb. Annals of 20: 453^62.
Botany91: 547-557. Morales-Ramos, J. A. and J. R. Cate. 1992. Functional
Beukeboom,L.W.,A.Kamping,andL.vandeZande. responseofCatolaccusgrandis(Burks)(Hymenop-
2007.Sexdeterminationinthehaplodiploidwasp tera: Pteromalidae) in field cages. Biological
Nasonia vitripennis (Hymenoptera: Chalcidoidea): Control 2: 193-202.
A critical consideration of models and evidence. , M. G. Rojas, J. Roberson, R. G. Jones, E. G.
Seminars in Cell and Developmental Biology 18: King, K. R. Summy, and J. R. Brazzel. 1994.
371-378. Suppressionofthebollweevilfirstgenerationby
Beye,M., M. Hasselman,M. K. Fondrk, R. E. PageJr, augmentative releases of Catolaccus grandis in
and S. W. Omholt. 2003. The Gene csd is the Aliceville,Alabama. Pp. 958-961in: 2994Proceed-
primary signal for sexual development in the
ings of the Beltwide Cotton Conferences Vol. 2.
honeybee and encodes an SR-type protein. Cell National Cotton Council of America, Memphis,
114: 419^29. TN.
Bull,BJ.eJn.j19a8m3.inEv/oCluutmimoninofgSsexPDuebtelrimsihniinnggMCecohmapnaisnmys,. , K. R. Summy, and E. G. King. 1995a.
Estimating parasitism by Catolaccus grandis (Hy-
Menlo Park, CA.
Cate, R. 1987. A method of rearing parasitoids of menoptera:Pteromalidae)afterinundativereleas-
J. es against the boll weevil (Coleoptera: Curculio-
boll weevil without the host plant. Southwestern
nidae). Environmental Entomology24: 1718-1725.
CastrEon,tLo.moR.loagnyd12D:ow21t1o-n2,15M..2005.Thepositionofthe ,M. G. Rojas,andE. G. King. 1995b. Venomof
Catolaccus grandis (Hymenoptera: Pteromalidae)
Hymenoptera within the Holometabola as in-
ferred from the mitochondrial genome of Perga and its role in parasitoid development and host
condei (Hymenoptera: Symphyta: Pergidae). Mo- regulation. Annals of the Entomological Society of
America 88: 800-808.
lecularPhylogeneicsand Evolution 34: 469-479.
Cook,J.M.andR.H.Crozier. 1995.Sexdetermination 199,8M..PoGt.enRtoijaals,usRe. Jo.fCionlevmiatrno,-raenardedE.CaGt.olKaicncgu.s
and population biology in Hymenoptera. Trends
grandis (Hymenoptera: Pteromalidae) for biolog-
in Ecologyand Evolution 10: 281-286.
Cowarne,prDo.ducP.tiavenddiJ.plKo.idStaahnldhuth.ap2l0o0i4d. mFaulncetsioinnalalny Cicuarlculcioonntirdoale)o.fJtouhrenablololf wEeceonvoimlic(CEonlteoompotleorag:y
inbreeding hymenopteran with complementary 91: 101-109.
sex determination. Proceedings of the National Ode, P. J., M. F. Antolin, and M. R. Strand. 1995.
Academy ofSciences ofthe United States ofAmerica Broodmate avoidance in the parasitic wasp
101: 10374-10379. Bracon hebetor. Animal Behavior49: 1239-1248.
Dobsgoenn,oSm.iLc.ainmdprMi.ntAi.ngTansoexuyed.et1e9r9m8i.nEavtiidonencmeecfhora-a PaxtoTne,ngRo..J2.,00P0..AM.icrTohsoarteenll,itNe.DGNylAleannsatlryasnids,raevnedalJs.
nism in Nasonia vitripennis (Hymenoptera; Chal- low diploid male production in a communalbee
cidoidea). Genetics 149: 2333-242. with inbreeding. Biology Journal of the Linnaean
Galbraith, D. W., K. R. Harkins,J. M. Maddox, N. M. Society69: 945-959.
Ayres, D. P. Sharma, and E. Firoosabady. 1983. Rasch, E. M., J. D. Cassidy, and R. C. King. 1975.
Rapidflowcytometricanalysisofthecellcyclein Estimatesofgenomesizeinhaplodiploid species
intactplanttissues. Science220: 1049-1051. of parasitoid wasps. Journal ofHistochemistry and
Gomez, T. V., N. M. Barcenas, and E. G. King. 1997. Cytochemistry23: 317.
Longevidad y capacidad de inseminacion de Ross, K. G., E. L. Vargo, L. Keller, and J. C. Trager.
machos de Catolaccus grandis (Burks) (Hyme- 1993.Effectofafoundereventonvariationinthe
noptera: Pteromalidae), parasitoide del picudo genetic sex-determining system of the fire ant
del aigodon Anthonomus grandis Boheman Solenopsis invicta. Genetics 135: 843-854.
(Coleoptera: Curculionidae). Memorias del XX Schrempf, A., S. Aron, and J. Heinze. 2006. Sex
CongresoNacionaldeControlBiologico. Guadalajara, determination and inbreeding depression in an
Jal. 13-14denoviembre de 1997: 102-104. antwithregularsib-mating. Heredity97: 75-80.
Volume 17, Number2, 2008 209
Stouthamer, R. and D. J. Kazmer. 1994. Cytogenetics Trent, C, C. Crosby, and J. Eavey. 2006. Additional
of microbe-associated parthenogenesis and its evidence for the genomic imprinting model of
consequences for gene flow in Trichogramma sex determination in the haplodiploid wasp
wasps. Heredity 73: 317-327. Nasonia vitripennis: isolationofbiparentaldiploid
,R.F.Luck,andJ.H.Werren. 1992.Geneticsof males after X-ray mutagenesis. Heredity 96:
sex determination and the improvement of 368-376.
biological control using parasitoids. Environmen- White, M. J. D. 1973. Animal Cytology and Evolution.
tal Entomology21: 427-435. 3rd ed. Cambridge University Press, Cambridge,
Summy, K. R., J. A. Morales, and E. G. King. 1995. U.K.
Suppressionofbollweevil(Coleoptera:Curculio- Whiting, P. W. 1943. Multiple alleles in complemen-
nidae) infestations on south Texas cotton by tarysexdeterminationofHabrobracon. Genetics28:
augmentative releases of the parasite Catolaccus 365-382.
grandis (Hymenoptera: Pteromalidae). Biological Woyke, J. 1963. What happens to the diploid drone
Control5: 523-529. larvae ina honeybee colony.Journal ofApiculture
, J. A. Morales-Ramos, and E. G. King. 1997. Research 19: 89-95.
Suppression of boll weevil infestations (Coleop- Wu, Z., K. R. Hopper, P. J. Ode, R. W. Fuester, M.
tera: Curculionidae) occurring on fallow-season Tuda, and G. E. Heimpel. 2005. Single-locus
cottoninSouthernTexasbyaugmentativereleas- complementary sex determination absent in
es of Catolaccus grandis (Hymenoptera: Pteroma- Heterospilus prosopidis (Hymenoptera: Braconi-
lidae). Biological Control 9: 209-215. dae). Heredity95: 228-234.