BIOGEOGRAPHY OF ASEXUAL AND SEXUAL REPRODUCTION IN CALOGLOSSA (DELESSERIACEAE,RHODOPHYTA) FROM AUSTRALIA AND NEW ZEALAND

Caloglossa species are widely distributed in mangroves and salt marshes around the world and their life history patterns are being investigated in laboratory culture. In Australia all isolates of C. monosticha, C. postiae and C. ogasawaraensis have Polysiphonia‐type (P‐type) sexual life histories. Among the 70 C. leprieurii isolates from Australia and New Zealand P‐type sexual reproduction also is dominant. However, ten isolates of C. leprieurii from the Spencer Gulf and the Gulf of St. Vincent in South Australia give rise to successive tetrasporphyte generations without gametophytes. Moreover, one isolate from Queensland is asexual. Only one South Australia isolate, obtained from Lake Alexandrina at the mouth of the Murray River, is sexual. South Australia and Pacific Mexico are two regions in which asexual reproduction is dominant. In another mangrove dwelling red alga Bostrychia moritiziana (Rhodomelaceae) non‐sexual reproduction also is frequent in Australia, New Caledonia and Bali (Indonesia). This asexual reproductive pattern of tetrasporophytic recycling appears to have arisen independently among individual populations of various red algal species in different regions. Investigations are underway on the molecular phylogeny of the Caloglossa leprieurii isolates.     

Reproductive patterns of Caloglossa species (Delesseriaceae, Rhodophyta) from Australia and New Zealand: multiple origins of asexuality in C. leprieurii. Literature review on apomixis, mixed-phase, bisexuality and sexual compatibility

Reproduction and life history patterns in culture of five Caloglossa speaes from Australia and New Zealand are compared. Caloglossa adhaerens King et Puttock and Caloglossa bengalensis (Martens) King et Puttock have a Polyslphonla‐type sexual life history (P‐type, isomorphic alternation of generations). Caloglossa monosticha Kamiya occurs only in Western Australia (WA) and is a P‐type. Caloglossa ogasawaraensis Okamura occurs in WA, Northern Territory (NT), Queensland (QLD), New South Wales (NSW), Victoria (VIC) and South Australia (SA) and is for the most part a P‐type in culture. A few isolates have bisexual gametophytes that are self‐compatible, while most are unisexual. Caloglossa ogasawaraensis from Adelaide, SA and from Wilsons Promontory, VIC are new records for these States. In Australia, Caloglossa postiae (King et Puttock) Kamiya et King occurs in NSW, NT and QLD. All nine isolates are P‐type. Isolates of Caloglossa leprieurii (Montagne) G. Martens from NSW, NT, QLD, Tasmania, VIC and New Zealand are P‐type except for the freshwater isolates in which tetraspore germlings do not reproduce. In some isolates mixed‐phase reproduction is seen with male gametophytes producing both viable spermatia and tetrasporangia and female gametophytes producing procarps and sori with non‐dividing sporangia. All isolates of C. leprieurii irom Spencer Gulf and Gulf of St Vincent, SA and one isolate from QLD give rise to successive asexual generations of tetrasporophytes. Based on RuBisCO spacer DNA data an asexual life history has arisen several times in the C. leprieurii complex. The literature on apomixis, mixed‐phase reproduction, bisexuality and sexual compatibility in red algae is surveyed.     

Biogeography of sexual and asexual populations in Bostrychia moritziana (Rhodomelaceae, Rhodophyta)

Bostrychia moritziana (Sonder ex Kützing) J. Agardh is recorded from many regions around the world. Our laboratory culture investigations have verified a sexual life cycle in isolates from Australia, Venezuela, Colombia, South Africa, Fiji, New Zealand and Indonesia. By contrast, asexual isolates producing successive generations of tetrasporophytes in laboratory culture and, presumably, in the field, are known from Australia. New Caledonia and Japan. In Australia, asexual reproduction is absent only in Victoria. In Western Australia, Northern Territory and Queensland, 99% of the isolates have asexual reproduction. In New South Wales (NSW), asexual and sexual populations are often intermixed. Of the 176 worldwide field collections, 58% were vegetative, 39% were tetrasporic, 2% were female and 1% were male. After several years of observations on the asexual isolates in culture, at least 30 successive asexual tetrasporophytic generations have developed. Only two asexual isolates (3558 and 3575) from NSW have formed a single male and female gametophyte in culture. In a self-cross of 3568, the carpospores developed into tetrasporophytes that recycled asexually. All outcrosses done with normal sexual isolates produced normal carposporophytes and the carpospores developed into tetrasporophytes that also recycled asexually. Asexual populations may arise repeatedly by loss of meiosis in tetrasporangia of sexual populations. Asexual reproduction apparently does not diminish the overall dispersal and abundance in the field. Our present bio-geographic data show that sexually reproducing popuiations of B. moritziana occur worldwide, while asexuaily reproducing populations are confined to the western Pacific. Bostrychia bispora West et Zuccarello, initially described on the basis of its asexual reproduction to distinguish it from B, moritziana, is now reduced to synonymy with B. moritziana.     

Caloglossa intermedia, sp. nov. (Rhodophyta) from the western atlantic coast: molecular and morphological analyses with special reference to C. leprieurii and C. monosticha

Caloglossa intermedia , sp. nov. is described from estuaries and salt marshes of Atlantic North America. This species is related to C. leprieurii (Montagne) G. Martens based on the position of rhizoids, whereas it is more similar to C. monosticha Kamiya in the number of cell rows at the nodes. Rhizoidal development of this alga also shows an intermediate characteristic between C. leprieurii and C. monosticha. Crosses were successful between the strains of C. intermedia from Georgia and South Carolina, but neither strain was interfertile with morphologically related species. C. intermedia from Georgia, New Jersey, and South Carolina had identical DNA sequences in the Rubisco spacer and flanking regions of rbc L and rbc S. This alga was more closely related to C. leprieurii in a molecular phylogenetic analysis. The evolution of each morphological character is discussed.     

EVOLUTIONARY DIVERGENCE IN THE RED ALGAE CALOGLOSSA LEPRIEURII AND C. APOMEIOTICA

Morphological comparisons, hybridization experiments, and molecular phylogenetic analyses using the RUBISCO spacer region were undertaken on 12 populations of Caloglossa leprieurii (Montagne) J. Agardh in order to clarify their relationships. In addition, data from one population of the morphologically similar but asexual species, C. apomeiotica (West et Zuccarello), were included in the assessment. Three morphological types were recognized on the basis of the number of cell rows at nodes of the main axis opposite to the lateral branch and blade width: single/ broad (with three mating groups), multiple/broad (three mating groups) and multiple/slender (one mating group). In the molecular analyses, C. leprieurii was resolved as two clusters that correspond phenetically to the single and multiple cell row types. Both the morphological and molecular data indicate that the asexual species was derived from sexual plants of the multiple cell row type. The reproductive compatibility correlates with genetic distance rather than geographical distance. Sympatric mating groups are completely incompatible and have 10–21 nucleotide changes in the examined region, whereas mating groups that produce abnormal progeny or pseudocystocarps are allopatrically distributed with 5–7 nucleotide changes. The present data suggest that the two populations, one with single and the other with multiple cell rows, which are sympatrically distributed in southeastern Japan, have probably evolved by allopatric speciation. The single/broad type that is restricted to the western Pacific, may have diverged genetically between eastern and western Australia, with subsequent dispersal from the western population as far as Japan.     

A mitochondrial marker for red algal intraspecific relationships

Intraspecific studies of red algae have relied on nuclear or plastid markers rather than mitochondrial data to address questions of systematics, biogeography or population genetics. In this study, primers were developed that spanned the noncoding intergenic region between the mitochondrial cytochrome oxidase subunit 2 and cytochrome oxidase subunit 3 genes. These primers were demonstrated to be successful on a variety of red algae in different orders: Gracilariales, Bonnemaisoniales and Ceramiales (families: Delesseriaceae, Ceramiaceae and Rhodomelaceae). Amplification products were between 450 and 320 bp in length, with variation in length shown among geographically distant isolates within a species. The region was variable within a single species, as shown for Bostrychia moritziana and B. radicans, and within populations of Caloglossa leprieurii. In the latter species, four mitochondrial haplotypes were observed in isolates from a single locality in Woolooware Bay, New South Wales, Australia. Analysis of hybrids between different mitochondrial haplotypes of B. moritziana revealed that the mitochondria are maternally inherited in this species. This is the first report of a mitochondrial marker that is variable within red algal populations and may lead to a better understanding of the population ecology of these important marine organisms.     

Marginal distribution and high heterozygosity of asexual Caloglossa vieillardii (Delesseriaceae,Rhodophyta) along the Australian coasts

In animals and land plants, many asexual species originate through inter‐ or intraspecific crosses, and such heterozygous asexuals frequently are more abundant than their sexual relatives in marginal habitats. Although asexual species have been reported in various macroalgal taxa, detailed information regarding their distribution, heterozygosity, and origin is limited. Because many asexual tetrasporophyte strains of Caloglossa vieillardii have been isolated from South Australia, far from their core tropical habitats, we re‐examined the distribution range of asexual C. vieillardii and genotyped these and other western Pacific strains using an actin gene marker. We confirmed the marginal distribution of the asexuals; however, a small patch of sexual thalli was newly discovered 450 km further west from asexual populations in South Australia. Three heterozygous genotypes and one homozygous genotypes were detected from nine asexual populations; 21 heterozygous strains were obligately asexual, but one homozygous strain suddenly produced sexual gametophytes after several years of culture. We hypothesized that the most abundant heterozygous genotype (defined as type 3/4) in asexual populations occurred by a cross between type 3 and type 4 allele gametophytes, both of which were isolated from the Australian coasts. In the crossing experiments, certain combinations between type 3 females and type 4 males produced tetrasporophytes, which recycled successive tetrasporophytes. In the culture experiments, whereas both sexual and asexual strains successfully produced tetraspores at 12°C, no sexual strains released carpospores below 14°C. However, it is uncertain whether this slight difference of maturation temperature was related to the marginal distribution of asexual C. vieillardii.     

COMPARATIVE MORPHOLOGY, CROSSABILITY, AND TAXONOMY WITHIN THE CALOGLOSSA CONTINUA (DELESSERIACEAE, RHODOPHYTA) COMPLEX FROM THE WESTERN PACIFIC

Systematic studies were undertaken on the Caloglossa continua ( Okamura) King et Puttock complex from Japan, Singapore, and Australia, based on morphology and reproductive compatibility. Specimens from Japan had two to six cell rows derived from a nodal axial cell, at the margin opposite the branch, whereas those from Australia possessed only a single cell row. Specimens from Singapore formed one to four cell rows per nodal axial cell and always contained at least one single cell row on any one thallus. These differences were maintained in cultured materials over a range of temperatures or salinities. Type material of C. continua had the same morphology as the Japanese specimens in this study. Carpospores discharged from the Japanese isolate germinated at 10°C, whereas those from Singapore and Australia died at this temperature. In hybridization experiments, the Japanese entity was completely nonfertile with both the Singaporean and Australian isolates. Many pseudocystocarps were produced in the crossing between the male from Australia and the female from Singapore, although the reciprocal combination did not produce any such structures. On the basis of the discontinuous morphology coupled with the complete reproductive isolation, the entities from Singapore and Australia are described here as C. monosticha sp. nov. The entities with multiple cell rows likely expanded their geographic range from tropical regions, where the majority of Caloglossa species are now distributed, to high-latitude regions, and such an expansion would be associated with acquiring low-temperature tolerance .     

EFFECTS OF SALINITY ON THE DISTRIBUTION OF CALOGLOSSA LEPRIEURII (RHODOPHYTA) IN THE BRISBANE RIVER,AUSTRALIA1

The role of salinity as a factor determining the distribution of two red algal taxa, Caloglossa leprieurii (Mont.) J. Ag. var. leprieurii and Caloglossa leprieurii var. angusta Jao, along the course of the Brisbane River, Queensland, Australia, was investigated. In the field, C. leprieurii var. angusta tolerated a narrower salinity range (mean salinity = 0.0–18.9) than C. leprieurii var. leprieurii (mean salinity = 2.0–33.8) and occupied areas of lower salinity (salinity expressed according to the Practical Salinity Scale of 1978). Both taxa coexisted for a distance of 23 km along the middle reaches of the river. Cell measurements of specimens of both taxa collected along the river showed an increase in cell sizes upstream from the mouth. Results of a reciprocal transplant experiment and growth responses in a series of laboratory culture studies of the two taxa in a range of salinities are presented. These could be correlated with the field distribution of the algae, demonstrating their euryhalinity and the presence of distinct salinity ecotypes.     

Ecological Characteristics of Macroalgae in Mangrove Forests in Fujian,China

The flora and distribution of macroalgae as well as the biomass of its two dominant species were studied in mangrove forests in Fujian Province, China. There were totally 42 species belonging to 24 genera of macroalgae, in which 15 species/8 genera belonged to Cyanophyta, 7/3 to Rhodophyta, and 20/13 to Chlorophyta. The biomass of the dominant species Caloglossa leprieurii and Catenella impudica were 2.22 to 8.44 g/m2 DW and 2.69 g/m2 DW in June,and 0.15 to 0.20 g/m2 DW and 2.12 g/m2 DW in December, respectively. On the tnmk surface of the mangrove plants,macroalgae appeared vertically to be distributed from lower upwards into six belts, namely Vaucheria sp. belt, Catenella impudica belt, Caloglossa ogasawaraensis-Bostrychia mixta belt, Calogiossa leprieurii belt, Chaetomorpha macrotona-Rhizoclonium riparium belt, and Chlorococcum sp. belt.     

90 Initial characterization of the terminal domains of linear plasmid-like dna''s from ernodesmis verticillata (chlorophyta)

Phylogenetic analyses inferred from rbcL sequences indicates that specimens of Caloglossa (Harvey) G. Martens collected from Vermilion Bay, Louisiana and Galveston, Texas, reported as C. leprieurii (Montagne) G. Martens (1869) constitutes a separate taxon. Studies are presently being conducted to compare this northwestern Gulf of Mexico taxon with material of C. intermedia Kamiya et West in Kamiya et al. (2000, J. Phycol. 36:411-420) from the Western Atlantic coast and with C. apomeiotica West et Zuccarello in West et al. (1994, Bot. Mar. 37:381–390) from Baja California, Mexico.     

福建红树林区大型藻类的生态学研究

主要研究中国福建省红树林区大型藻类分布、优势种的生物量和林冠下藻种的垂直分布特点。结果表明:福建红树林区的大型藻类有24属42种,其中蓝藻8属15种、红藻3属7种、绿藻13属20种。优势种中鹧鸪菜(Caloglossa leprieurii)和节附链藻(Catenella impudica)的生物量在6月分别为2.22～8.44g/m~2 DW和2.69g/m~2 DW,在12月分别为0.15～0.20g/m~2 DW和2.12g/m~2 DW。红树林中树干上附着生长的大型藻类的垂直分布自下而上可分成6个带:1.无隔藻(Vaucheria sp.)带;2、节附链藻带;3.侧枝鹧鸪菜-混合卷枝藻(Caloglossa ogasawaraensis-Bostrychia mixta)带;4.鹧鸪菜带;5.硬毛藻-岸生根枝藻(Chaetomorpha macrotona-Rhizoclonium riparium)带;6.绿球藻(Chlorococcum sp.)带。     

Reproductive biology of Stictosiphonia hookeri (Rhodomelaceae,Rhodophyta) from Argentina,Chile, South Africa and Australia in laboratory culture

The red alga Stictosiphonia hookeri is epilithic in shaded habitats of the upper intertidal zone from 30 to 55° S. Thalli of this species from Argentina, Chile, South Africa and Australia, usually without reproductive structures when collected, all developed tetrasporangia in culture. Although good vegetative growth occurred in all nine isolates at 20–25 °C, 12:12 light: dark cycle, 10–30 µmol photons m^–2 s^–1, none reproduced in these conditions except one isolate from Australia. At 15 °C the four South African (34 °S) isolates developed tetrasporangial stichidia, and three completed a Polysiphonia-type life history. Gametophytes were unisexual or bisexual. At 15 °C one isolate from Chile (36 °S) formed tetrasporangia, but sporelings were not viable. At 10 °C isolates from Argentina and Chile (53 °S and 54 °S) formed tetrasporangia; however, only the Chile isolate completed a Polysiphonia-type life history with unisexual gametophytes. The temperature required to induce sporogenesis correlates with the range of water and air temperatures in the natural habitats of each isolate. In irradiances >50 µmol m^–2 s^–1 the thalli became yellow- brown within two weeks because of phycobiliprotein loss, but this did not impair growth or reproduction. The Argentina and Chile isolates were resistant to freezing in seawater for at least two days, showing no cell damage. The protein cuticle of the outer cell wall is repeatedly shed in culture. This may serve to minimize the attachment of epiphytes in the field.     

Sexual and asexual reproduction of the holothurian Stichopus chloronotus (Echinodermata): a comparison between La Réunion (Indian Ocean) and east Australia (Pacific Ocean)

Summary

Stichopus chloronotus (Brandt, 1835) is one among nine aspidochirotide holothurian species known to reproduce both sexually by broadcast spawning and asexually by transverse fission. New data on the sexual cycle of this species in La Réunion are presented here and information available on sexual and asexual reproduction in this species is summarised. Sexual reproduction on La Réunion shows a distinct seasonality with a main spawning period in the warm season (November-February). The spawning period the Great Barrier Reef appears to be at the same time. Some intriguing deviations from unity in sex-ratio, usually biased towards more male individuals, have been observed in both geographic regions (sex ratio at La Reunion 31:1). New data on the asexual reproduction of this species in La Réunion confirm the high rates of fission. The peak of asexual reproduction in both the Indian and Pacific Ocean was observed in winter (June-July). Thus, asexual reproduction in this species occurs outside the season for sexual reproduction. The rate of asexual reproduction appears to vary between sample locations. However, results of population genetic studies on S. chloronotus (Uthicke et al., 1999; Uthicke et al., 2001) indicated that in most populations investigated a maximum of about 60% of all individuals may be derived from sexual recruitment. Cluster analyses on genetic distances between populations grouped populations within Oceans together, with the exception of one sample from a nearshore reef of the GBR. Although genetic differences between the two regions exist, these are relatively small regarding the large geographic distance. We conclude that asexual reproduction in S. chloronotus is important to maintain local population sizes, but that larval exchange between populations mediated by sexual reproduction is important for colonisation of new areas and to provide connectivity between populations. Here, we present the first synthesis of these phenomena for a holothurian species.     

Geographically diverse Australian isolates of Melissococcus pluton exhibit minimal genotypic diversity by restriction endonuclease analysis

Melissococcus pluton, the causative agent of European foulbrood is an economically significant disease of honey bees (Apis mellifera) across most regions of the world and is prevalent throughout most states of Australia. 49 Isolates of M. pluton recovered from diseased colonies or honey samples in New South Wales, Queensland, South Australia, Tasmania and Victoria were compared using SDS-PAGE, Western immunoblotting and restriction endonuclease analyses. DNA profiles of all 49 geographically diverse isolates showed remarkably similar AluI profiles although four isolates (one each from Queensland, South Australia, New South Wales and Victoria) displayed minor profile variations compared to AluI patterns of all other isolates. DNA from a subset of the 49 Australian and three isolates from the United Kingdom were digested separately with the restriction endonucleases CfoI, RsaI and DraI. Restriction endonuclease fragment patterns generated using these enzymes were also similar although minor variations were noted. SDS-PAGE of whole cell proteins from 13 of the 49 isolates from different states of Australia, including the four isolates which displayed minor profile variations (AluI) produced indistinguishable patterns. Major immunoreactive proteins of approximate molecular masses of 21, 24, 28, 30, 36, 40, 44, 56, 60, 71, 79 and 95 kDa were observed in immunoblots of whole cell lysates of 22 of the 49 isolates and reacted with rabbit hyperimmune antibodies raised against M. pluton whole cells. Neither SDS-PAGE or immunoblotting was capable of distinguishing differences between geographically diverse isolates of M. pluton. Collectively these data confirm that Australian isolates of M. pluton are genetically homogeneous and that this species may be clonal. Plasmid DNA was not detected in whole cell DNA profiles of any isolate resolved using agarose gel electrophoresis.     

COMPARATIVE STUDIES ON THE CELL WALLS OF SEXUAL AND ASEXUAL BANGIA ATROPURPUREA (RHODOPHYTA). I. HISTOCHEMISTRY OF POLYSACCHARIDES1

A comparative histochemical study of the nature and distribution of acidic and neutral cell wall polysaccharides was conducted on marine sexual and asexual filaments of the red alga Bangia atropurpurea (Roth) C. Ag. Outer and inner walls of this species were clearly partitioned according to staining and transmission electron microscopic characteristics. Neutral polysaccharides were detected in the outer coating (cuticle) but were absent from outer and inner walls of all filaments. Acidic polysaccharides were noted in the outer wall material but not in the inner wall layers of any filaments at any developmental stages. The major staining component of vegetative regions of sexual material and all regions of asexual filaments was a highly sulfated polymer. During sexual reproduction only there was a generalized change in the nature of the acidic component, characterized by a decrease in intensity of staining for sulfates in both male and female filaments and the appearance, in female filaments only, of polysaccharides which presumably were carboxylated. Spermatia attached to both male and female filaments in regions where sexual differentiation was initiated and where changes in the outer wall components commenced.     

Observations on Bostrychia radicosa comb. nov. (Rhodomelaceae, Rhodophyta)

Only two genera in the Rhodomelaceae share the morphological character of transverse division of periaxial cells into two or more tier cells in which the pit connection is retained between the lower cell and the axial cell: Bostrychia and Rhodolachne. One species, Rhodolachne radicosa Itono, has been reported from mangroves, a common habitat for Bostrychia. Many collections of an entity similar to Rhodolachne radicosa have been made from localities around the Indo‐Pacific. Culture observations show a Polysiphonia‐type sexual life history in Malaysia and New Caledonia isolates that produce self‐compatible bisexual gametophytes. The New Caledonia isolate also has unisexual gametophytes. An isolate from New South Wales (Australia) reproduces asexually through successive generations of tetrasporophytes. The Thailand isolate has successive generations of mixed‐phase tetrasporophytes. The tetrasporangial stichidia also bear male spermatangial sectors, but female structures are lacking. Western Australia and Madagascar isolates do not reproduce in culture. Molecular evidence, based on sequencing of the rbcL and the large subunit ribosomal RNA genes, shows that these isolates belong to the genus Bostrychia. Low molecular weight carbohydrate analysis reveals high levels of digeneaside in all isolates. The sugar hexitol sorbitol, an osmolyte characteristic of Bostrychia, occurs in all isolates, whereas the Madagascar and New Caledonia isolates have very low levels of dulcitol. Molecular, low molecular weight carbohydrate and morphological evidence show that Rhodolachne radicosa belongs within the genus Bostrychia. We transfer Rhodolachne radicosa to Bostrychia radicosa (Itono) West, Zuccarello and Hommersand.     

COMPARATIVE STUDIES ON THE CELL WALLS OF SEXUAL AND ASEXUAL BANGIA ATROPURPUREA (RHODOPHYTA). II ELECTROPHORETIC PATTERNS OF POLYSACCHARIDES1

Cellulose acetate electrophoresis of the hot water soluble polysaccharide extracts from whole filaments, as well as base, mid and tip segments, of marine asexual and sexual Bangia atropurpurea (Roth) C. Ag. Yielded distinctive patterns which demonstrated that changes occur in the outer cell walls during sexual reproduction. Heterogeneity of the sulfated polysaccharide components isolated from outer cell walls was shown to be specifically related to sexual reproduction. Two components (Band I and II) were detected in extracts from tips of sexual filaments, whole only one (Band I) was present in the vegetative segments of all filaments and in asexual reproductive regions. The faster running component (Band II) was detected during the later stages of sexual development, prior to maturation.     

Electrophoretic studies of Australasian, North American and European isolates of Sclerotinia sclerotiorum and related species.

Forty-seven isolates of Sclerotinia species, collected from a variety of crops growing in Australia, New Zealand, North America and Europe, have been classified into three distinct groups on the electrophoretic patterns for soluble proteins, arylesterase, acid phosphatase, tetrazolium oxidase, glucose-6-phosphate dehydrogenase (NADP-linked) and reduced nicotinamide adenine dinucleotide phosphate dehydrogenase. There were only small intra-group differences. The electrophoretic patterns of an isolate of Whetzelinia (= Sclerotinia) tuberosa were characteristically different from those of the other isolates. These results support the findings from previous studies when ontogenetic, electrophoretic and mycelial-interaction criteria were used to group a smaller number of isolates from New South Wales, Australia. It is concluded that S. sclerotiorum, S. trifoliorum and S. minor are three distinct species.     

Isolates of Cryptococcus neoformans from infected animals reveal genetic exchange in unisexual, alpha mating type populations

Sexual reproduction and genetic exchange are important for the evolution of fungal pathogens and for producing potentially infective spores. Studies to determine whether sex occurs in the pathogenic yeast Cryptococcus neoformans var. grubii have produced enigmatic results, however: basidiospores are the most likely infective propagules, and clinical isolates are fertile and genetically diverse, consistent with a sexual species, but almost all populations examined consist of a single mating type and have little evidence for genetic recombination. The choice of population is critical when looking for recombination, particularly when significant asexual propagation is likely and when latency may complicate assessing the origin of an isolate. We therefore selected isolates from infected animals living in the region of Sydney, Australia, with the assumption that the relatively short life spans and limited travels of the animal hosts would provide a very defined population. All isolates were mating type α and were of molecular genotype VNI or VNII. A lack of linkage disequilibrium among loci suggested that genetic exchange occurred within both genotype groups. Four diploid VNII isolates that produced filaments and basidium-like structures when cultured in proximity to an a mating type strain were found. Recent studies suggest that compatible α-α unions can occur in C. neoformans var. neoformans populations and in populations of the sibling species Cryptococcus gattii. As a mating type strains of C. neoformans var. grubii have never been found in Australia, or in the VNII molecular type globally, the potential for α-α unions is evidence that α-α unisexual mating maintains sexual recombination and diversity in this pathogen and may produce infectious propagules.