Phylogenetic structure of the Sphaeriinae, a global clade of freshwater bivalve molluscs, inferred from nuclear (ITS-1) and mitochondrial (16S) ribosomal gene sequences

The Sphaeriidae represent one of the primary molluscan radiations into freshwater environments. We have reconstructed phylogenetic relationships of the Sphaeriinae, a cosmopolitan sphaeriid subfamily, using variation in nuclear ribosomal first internal transcribed spacer (ITS-1) and mitochondrial large ribosomal subunit (16S) gene fragments. A total of 38 New World, Eurasian and Antipodean taxa were characterized, including all primary taxonomic groupings except for Neopisidium , and members of the sister clade Euperinae were employed as outgroups. Phylogenetic analyses of individual and combined (16S + ITS1) datasets all recovered a paraphyletic Pisidium and a derived clade of asynchronous brooding Sphaerium / Musculium taxa. Maximum parsimony as well as maximum likelihood analyses of combined data yielded largely congruent and well-resolved topologies, and robustly supported clades were utilized to revise current sphaeriine taxonomy. Instead of the traditionally accepted three cosmopolitan genera, Pisidium s.l. , Musculium , and Sphaerium , five major monophyletic lineages, Afropisidium , Odhneripisidium , Pisidium , Cyclocalyx and Sphaerium , were recognized at the generic level. In addition, a number of subgeneric level groups were recovered in Sphaerium : Herringtonium , Sphaerium s . s ., Sphaerinova , Amesoda , and Musculium , together with one unassigned species, S. transversum .     

Phylogenetic analysis based on the morphology of viviparous freshwater clams of the family Sphaeriidae (Mollusca, Bivalvia, Veneroida)

The cosmopolitan viviparous bivalves of the family Sphaeriidae (fingernail clams) comprise not only some of the smallest freshwater molluscs, but also an abundant and ecologically important group that often dominates benthic communities of springs, ponds and swamps. The origin from marine ancestors and their subsequent evolution in limnic environments, in particular the development of distinct reproductive modes including complex parental care repertoires, are largely unresolved. This paper presents the results of a phylogenetic analysis of 69 morphological characters from 57 taxa (54 representing sphaeriids throughout the distribution area plus three outgroups). The heuristic search resulted in 753 most-parsimonious trees of length 154 [consistency index (CI) = 0.682, retention index (RI) = 0.906, rescaled consistency index (RC) = 0.618]. Only Pisidium of the three traditionally regarded constituent genera is supported as a monophyletic group; Sphaerium and Musculium in their traditional deliminations are found to be paraphyletic. Instead, the analysis supports a clade comprising all species of Musculium plus Pisidium as suggested by previous morphology-based classifications. However, the shortest tree alternatively supporting a Sphaerium  +  Musculium clade suggested by molecular data is only one step longer. Some clades that correspond to the subgeneric divisions of the three traditionally recognized sphaeriid genera are supported. Exclusion is suggested of the taxon Euperidae ( Eupera and Byssodonta , both with ovo-viviparous species) from the true Sphaeriidae that then comprises all species with eu-viviparous reproductive mode, i.e. brooding and nourishing their embryos in specialized brood pouches in the gills. The implications for the reconstruction of the evolutionary history of Sphaeriidae and the availability of existing taxonomic names for the systematization suggested by the present analysis are discussed.     

6-Phosphogluconate dehydrogenase (PGD) allele phylogeny is incongruent with a recent origin of polyploidization in some North American Sphaeriidae (Mollusca,Bivalvia)

Although polyploidization is rare among bivalve mollusks, recent cytogenetic studies have revealed a remarkable degree of genome amplification (up to 13n) in the freshwater bivalve family Sphaeriidae. We generated single-copy nuclear gene trees in order to test hypotheses addressing the evolutionary origins of sphaeriid genome duplication. Polyploid North American members of three cosmopolitan sphaeriid genera (Sphaerium, Musculium, and Pisidium) were characterized for their expressed allelic repertoire of a 526 nt c-DNA fragment of 6-phosphogluconate dehydrogenase (PGD). Pronounced levels of intra-individual genetic variation were uncovered in most of the polyploid taxa and a minority of alleles showed strong evidence of recombination. Phylogenetic analyses resolved polyploid sphaeriid PGD alleles into two clades (A, B), each of which contained a subsample of intra-individual allelic diversity of the genus Sphaerium. These two clades were also recovered in Musculium, however one (B) is represented here by a single recombinant allele. With the exception of a divergent segment in one putatively recombinant allele, the expressed PGD repertoire of the three Pisidium species investigated was restricted to one of the two clades (A). Major within-clade PGD gene tree branching patterns were congruent with mitochondrial gene tree topologies for these taxa. These results are inconsistent with a pattern of recent independent attainment of a polyploid status by our Sphaerium/Musculium study taxa and indicate that they may share a common genome duplication event predating the Miocene appearance of these two genera in the fossil record.     

Evolution of parental care and ovulation behavior in oysters

Approximately half of all living oysters brood offspring in the inhalant chamber of their mantle cavities; the remainder are broadcast spawners which do not engage in parental care of young. Ostreid ovulation involves a complex behavioral sequence that results in the countercurrent passage of newly spawned eggs through the gills (ctenidia) and into the inhalant chamber. We constructed molecular and combined-evidence phylogenetic trees to test hypotheses concerning the directionality of parental care evolution, and the evolutionary significance of the trans-ctenidial ovulation pathway, in the Ostreidae. Representatives of all three ostreid subfamilies, together with gryphaeid and nonostreoidean pterioid outgroups, were sequenced for a 941-nucleotide fragment of the 28S ribosomal gene. Our phylogenetic analyses indicate that (1) the Ostreidae are robustly monophyletic, (2) broadcast spawning and larval planktotrophy are ancestral ostreid traits, (3) trans-ctenidial ovulation predates the evolution of parental care in ostreid lineages, and (4) brooding originated once in the common ancestor of the Ostreinae/Lophinae, involved a modification of the final behavioral step in the ancestral ovulation pathway, and has been retained in all descendent lineages. Our data permit an independent test of fossil-based ostreid phylogenetic hypotheses and provide novel insights into oyster evolution and systematics.     

Pronounced karyological divergence of the North American congeners Sphaerium rhomboideum and S. occidentale (Bivalvia: Veneroida: Sphaeriidae)

Chromosome sets of two North American sphaeriid species, Sphaeriumrhomboideum Say, 1822 and S. occidentale Lewis, 1856, were studiedusing conventional Giemsa staining and karyometric analysis.Pronounced karyological divergence of congeners was revealed.The diploid number of 2n = 44 was reported for S. rhomboideumand this is the first record of a diploid species in the highlypolychromosomic Nearctic sphaeriid fauna. The karyotype wascharacterized by medium-sized and small chromosomes, which decreasedin size gradually from 5.77 to 1.9 µm. Biarmed chromosomeswith medially and submedially located centromeres predominated,but six pairs of subtelo-telocentric elements were also observedin the karyotype. The estimated mitotic chromosome number forS. occidentale ranges from 189 to 213, but most of the cellsexamined contained about 204–209 chromosomes. A firstattempt to karyotype a polyploid sphaeriid was made. It wasrevealed that the comparatively large and middle-sized chromosomescould be grouped in four, so the karyotype presumably evolvedthrough tetraploidization. The small chromosomes formed thelarge fraction, about 137. Due to their similar and indistinctmorphologies, it was impossible to arrange them into subgroupswith confidence. Revealed karyological characteristics are discussedwith reference to the existing phylogenetic interpretationsof the evolutionary history of the Sphaeriinae. (Received 8 November 2006; accepted 25 June 2007)     

The cost of being a caring mother: the ignored factor in the reproduction of marine invertebrates

Investment in reproduction ranges from gamete production to active parental care, and marine invertebrates span this range. However, the cost of parental care has not yet been systematically quantified, nor incorporated into life history studies of marine invertebrates, in contrast to most other animal taxa. Since oxygen is a limiting factor in egg masses of marine invertebrates, we studied patterns of oxygen partial pressure over time in embryo masses of Brachyuran crabs, and correlated these results with the cost of providing oxygen to the embryos. We found that: (1) oxygen is limiting in the embryo masses, (2) female crabs show an active brooding behaviour that we think helps to provide oxygen to the embryo mass, and (3) there is a substantial parental investment associated with brooding behaviours. Oxygen limitation and parental investment seem to be associated in many taxa of marine invertebrates, and we suggest that oxygen provision to the embryos may be a critical factor determining parental investment in this group.     

Male pregnancy in seahorses and pipefishes (family Syngnathidae): rapid diversification of paternal brood pouch morphology inferred from a molecular phylogeny

In contrast to the majority of vertebrate species, primary male parental care is common in fishes and encompasses a remarkable diversity of adaptations. Seahorses and pipefishes (Family Syngnathidae) exhibit some of the most specialized forms of paternal care in animals and so are ideally suited to the study of the evolution of male parental care. During mating, female syngnathids transfer eggs to specialized morphological structures that are located on either the abdomen or tail of the male. The male provides all postfertilization parental care and has morphological and physiological adaptations to osmoregulate, aerate, and even nourish the developing embryos. While all syngnathid species are adapted for paternal care, the brooding structure with which this is accomplished varies between species, from simple ventral gluing areas to much more complex structures such as the completely enclosed pouches of the seahorses. Our combined cytochrome b-, 12S rDNA-, and 16S rDNA-based molecular phylogeny of syngnathid fishes demonstrates that rapid diversification of male brooding structures has been associated with the major evolutionary radiation of the group, suggesting that development and diversification of structures involved in paternal care may have been key evolutionary innovations of the Syngnathidae. Molecular analyses also highlight geographical centers of biodiversity and suggest interoceanic migration of Syngnathus pipefishes from their center of origin in the Pacific.     

Exclusive Male Egg Care and Determinants of Brooding Success in a Millipede

The evolution of exclusive male parental care is a major and controversial issue in behavioural ecology. Although arthropods practicing paternal care are thought to be key taxa for investigating this issue, few studies have attempted to clarify the selection factors associated with male behaviour and fitness consequences in arthropods. In the millipede Brachycybe nodulosa, males curl their bodies around egg masses on the undersides of decaying logs. Male‐removal experiments in the laboratory strongly suggest that males defend the eggs against fungal infection. Orphaned eggs were soon covered by hyphae and no eggs hatched, whereas almost all eggs brooded by males successfully hatched. The egg‐brooding males showed no aggressive responses when disturbed. Only some mature males bred in the field. Furthermore, the number of eggs brooded varied greatly among the males. Selected generalized linear models revealed that males with a wide seventh body segment, which possesses gonopods (genital legs), tended to succeed in brooding; and males with a wider body also obtained more eggs. Colony attributes had no significant effects on male brooding. We discuss the possible sexual selection mechanisms that could accomplish this pattern of brooding success among male B. nodulosa.     

King penguin brooding and defending a sub-Antarctic skua chick

Interspecific parental care is rare, conveys no ultimate evolutionary advantage, and is usually attributed to reproductive errors in species with analogous habitat, behaviour and diet. We report on interspecific parental care (brooding and “defence” of unrelated chick) provided by a king penguin to a sub-Antarctic skua chick on Marion Island, despite substantial risk of injury to the penguin due to the presence of the true parents.     

Temporal and spatial complexity of maternal thermoregulation in tropical pythons

Parental care is a widespread adaptation that evolved independently in a broad range of taxa. Although the dynamics by which two parents meet the developmental needs of offspring are well studied in birds, we lack understanding about the temporal and spatial complexity of parental care in taxa exhibiting female-only care, the predominant mode of parental care. Thus, we examined the behavioral and physiological mechanisms by which female water pythons Liasis fuscus meet a widespread developmental need (thermoregulation) in a natural setting. Although female L. fuscus were not facultatively thermogenic, they did use behaviors on multiple spatial scales (e.g., shifts in egg-brooding postures and surface activity patterns) to balance the thermal needs of their offspring throughout reproduction (gravidity and egg brooding). Maternal behaviors in L. fuscus varied by stage within reproduction and were mediated by interindividual variation in body size and fecundity. Female pythons with relatively larger clutch sizes were cooler during egg brooding, suggesting a trade-off between reproductive quantity (size of clutch) and quality (developmental temperature). In nature, caregiving parents of all taxa must navigate both extrinsic factors (temporal and spatial complexity) and intrinsic factors (body size and fecundity) to meet the needs of their offspring. Our study used a comprehensive approach that can be used as a general template for future research examining the dynamics by which parents meet other developmental needs (e.g., predation risk or energy balance).     

Evolution of mouthbrooding and life-history correlates in the fighting fish genus Betta

The origin of and evolutionary transitions among the extraordinary diverse forms of parental care in teleost fish remain largely unknown. The "safe harbor" hypothesis predicts that the evolution from a "guarding" to a "brooding" form of care in teleost fish is associated with shifts in reproductive and life-history features such as reduced fecundity, and increased egg volume with higher parental investment. Robust phylogenetic hypotheses may help to identify evolutionary changes in key traits associated with differences in the form of parental care. Here, we used reconstruction of ancestral character states to study the evolution of the two forms of parental care, bubble nesting and mouthbrooding in the fighting fish genus Betta. We also applied a comparative analysis using the phylogenetic generalized least-squares method to test the "safe harbor" hypothesis by evaluating differences between the two forms of parental care in standard length, life-history traits, and three habitat variables. Evolutionary hypotheses were derived from the first molecular phylogeny (nuclear and mitochondrial DNA sequence data; 4448 bp) of this speciose group. Ancestral character state reconstructions of the evolution of the form of parental care in the genus Betta, using the methods of unweighted parsimony and maximum likelihood, are uncertain and further indicate a high rate of evolutionary transitions. Applying different weights for the suspected directionality of changes, based on the consistent phenotypic and behavioral differences found between bubble nesters and mouthbrooders, recurrent origin of mouthbrooding in the genus Betta is favored using parsimony. Our comparative analyses further demonstrate that bubble nesters and mouthbrooders do not have a consistent set of life-history correlates. The form of parental care in Betta is correlated only with offspring size, with mouthbrooders having significantly bigger offspring than bubble nesters, but is not correlated with egg volume, clutch size, and broodcare duration, nor with any of the three habitat variables tested. Our results thus challenge the general predictions of the "safe harbor" hypothesis for the evolution of alternative brood care forms in the fighting fish genus Betta.     

A molecular phylogeny of annelids

We present parsimony analyses of annelids based on the largest taxon sample and most extensive molecular data set yet assembled, with two nuclear ribosomal genes (18S rDNA and the D1 region of 28S rDNA), one nuclear protein coding‐gene (Histone H3) and one mitochondrial ribosomal gene (16S rDNA) from 217 terminal taxa. Of these, 267 sequences are newly sequenced, and the remaining were obtained from GenBank. The included taxa are based on the criteria that the taxon must have 18S rDNA or at least two other loci. Our analyses show that 68% of annelid family ranked taxa represented by more than one taxon in our study are supported by a jackknife value > 50%. In spite of the size of our data set, the phylogenetic signal in the deepest part of the tree remains weak and the majority of the currently recognized major polychaete clades (except Amphinomida and Aphroditiformia) could not be recovered. Terbelliformia is monophyletic (with the exclusion of Pectinariidae, for which only 18S data were available), whereas members of taxa such as Phyllodocida, Cirratuliformia, Sabellida and Scolecida are scattered over the trees. Clitellata is monophyletic, although Dinophilidae should possibly be included, and Clitellata has a sister group within the polychaetes. One major problem is the current lack of knowledge on the closest relatives to annelids and the position of the annelid root. We suggest that the poor resolution in the basal parts of the trees presented here may be due to lack of signal connected to incomplete data sets both in terms of terminal and gene sampling, rapid radiation events and/or uneven evolutionary rates and long‐branch attraction. © The Willi Hennig Society 2006.     

Why care? Inferring the evolution of complex social behaviour

Phylogenetic comparative analyses of complex traits often reduce the traits of interests into a single (or a few) component variables. Here, we show that this may be an over‐simplification, because components of a complex trait may evolve independently from each other. Using eight components of parental care in 400 bird species from 89 avian families that represent the relative contribution of male vs. female to a particular type of care, we show that some components evolve in a highly correlated manner, whereas others exhibit low (or no) phylogenetic correlation. Correlations were stronger within types of parental activity (brooding, feeding, guarding) than within stages of the breeding cycle (incubation, prefledging care, post‐fledging care). A phylogenetically corrected cluster analysis identified two groups of parental care components that evolved in a correlated fashion: one group included incubation and brooding, whereas the other group comprised of the remaining components. The two groups of components provide working hypotheses for follow‐up studies to test the underlying genetic, developmental and ecological co‐evolutionary mechanism between male and female care. Furthermore, the components within each group are expected to respond consistently to different ambient and social environments.     

Phylogeny of Alariaceae, Laminariaceae, and Lessoniaceae (Phaeophyceae) based on plastid-encoded RuBisCo spacer and nuclear-encoded ITS sequence comparisons.

Concatenated sequences from the plastid-encoded RuBisCo spacer and nuclear-encoded rDNA ITS region of the Alariaceae, Laminariaceae, and Lessoniaceae as currently recognized were used to determine the phylogeny of kelps (Phaeophyceae). Our analyses indicate that all taxa in the Alariaceae, Laminariaceae, and Lessoniaceae form a monophyletic lineage (the Laminariales sensu stricto). The phylogenetic analyses show that the kelps form eight well-supported clades (represented by Egregia, Laminaria, Hedophyllum, Macrocystis, Alaria, Agarum, Ecklonia, and Lessonia) that conform to the tribes of the current morphological classification system of the "advanced" kelps. Our results suggest that the kelps should be classified into eight families rather than the three that are presently used. The interrelationships among the eight lineages were, however, unresolved in the phylogenetic analyses. In all trees, Egregia diverged first and is the sister to the other kelp taxa. Our phylogenetic analyses also indicate that Kjellmaniella and Laminaria do not form a monophyletic group. Taken together, the RuBisCo spacer and rDNA ITS prove useful for understanding the evolutionary history of the advanced kelps and provide a new framework for establishing the systematics of these commercially important brown algae.     

The relationship between female brooding and male nestling provisioning: does climate underlie geographic variation in sex roles?

Comparative studies of populations occupying different environments can provide insights into the ecological conditions affecting differences in parental strategies, including the relative contributions of males and females. Male and female parental strategies reflect the interplay between ecological conditions, the contributions of the social mate, and the needs of offspring. Climate is expected to underlie geographic variation in incubation and brooding behavior, and can thereby affect both the absolute and relative contributions of each sex to other aspects of parental care such as offspring provisioning. However, geographic variation in brooding behavior has received much less attention than variation in incubation attentiveness or provisioning rates. We compared parental behavior during the nestling period in populations of orange‐crowned warblers Oreothlypis celata near the northern (64°N) and southern (33°N) boundaries of the breeding range. In Alaska, we found that males were responsible for the majority of food delivery whereas the sexes contributed equally to provisioning in California. Higher male provisioning in Alaska appeared to facilitate a higher proportion of time females spent brooding the nestlings. Surprisingly, differences in brooding between populations could not be explained by variation in ambient temperature, which was similar between populations during the nestling period. While these results represent a single population contrast, they suggest additional hypotheses for the ecological correlates and evolutionary drivers of geographic variation in brooding behavior, and the factors that shape the contributions of each sex.     

Phylogenetic Relationships of Extinct Cetartiodactyls: Results of Simultaneous Analyses of Molecular, Morphological, and Stratigraphic Data

Although some recent morphological and molecular studies agree that Cetacea is closely related to Hippopotamidae, there is little consensus on the phylogeny within Cetartiodactyla. We addressed this problem by conducting two analyses: (1) a simultaneous cladistic analysis of intrinsic data (morphology and molecules) and (2) a stratocladistic analysis, which included morphological, molecular, and stratigraphic data. Unlike previous simultaneous analyses, we had the opportunity to include data from the recently described hindlimbs of protocetid and pakicetid cetaceans. Our intrinsic dataset includes 73 taxa scored for 8,229 informative characters, of which 208 are morphological and 8,021 molecular. Both analyses supported the exclusion of Mesonychia from Cetartiodactyla and a close phylogenetic relationship between Hippopotamidae and Cetacea. Many polytomies in the strict consensus of the most parsimonious trees for the intrinsic dataset can be attributed to differing positions for Raoellidae, which in some trees is the sister-group to Cetacea. Pruning Raoellidae and 18 other taxa from all most parsimonious produced a fully resolved agreement subtree, which indicates that the Old World taxa Cebochoerus and Mixtotherium are successive stem taxa to Whippomorpha (i.e., Cetacea + Hippopotamidae). The main result of adding stratigraphic information to the intrinsic dataset was that we found fewer most parsimonious trees, which in most respects were congruent with a subset of the shortest trees for the intrinsic dataset. Our stratocladistic analysis supports species of Diacodexis as the most basal cetartiodactyls, a clade of suiform cetartiodactyls, a monophyletic Tylopoda that includes Protoceratidae, and a monophyletic Carnivora. We were unable to identify any pre-Miocene stem taxa to Hippopotamidae, thus its ghost lineage is still 39 million years long. The relatively low Bremer support for many nodes in our trees indicates that our phylogenetic hypotheses should be subjected to further testing.     

Anchored hybrid enrichment provides new insights into the phylogeny and evolution of longhorned beetles (Cerambycidae)

Cerambycidae is a species‐rich family of mostly wood‐feeding (xylophagous) beetles containing nearly 35 000 known species. The higher‐level phylogeny of C erambycidae has never been robustly reconstructed using molecular phylogenetic data or a comprehensive sample of higher taxa, and its internal relationships and evolutionary history remain the subjects of ongoing debate. We reconstructed the higher‐level phylogeny of C erambycidae using phylogenomic data from 522 single copy nuclear genes, generated via anchored hybrid enrichment. Our taxon sample (31 C hrysomeloidea, four outgroup taxa: two C urculionoidea and two C ucujoidea) included exemplars of all families and 23 of 30 subfamilies of C hrysomeloidea (18 of 19 non‐chrysomelid C hrysomeloidea), with a focus on the large family C erambycidae. Our results reveal a monophyletic C erambycidae s.s. in all but one analysis, and a polyphyletic C erambycidae s.l. When monophyletic, C erambycidae s.s. was sister to the family D isteniidae. Relationships among the subfamilies of C erambycidae s.s. were also recovered with strong statistical support except for C erambycinae being made paraphyletic by Dorcasomus A udinet‐S erville (D orcasominae) in the nucleotide (but not amino acid) trees. Most other chrysomeloid families represented by more than one terminal taxon – C hrysomelidae, D isteniidae, V esperidae and O rsodacnidae – were monophyletic, but M egalopodidae was rendered paraphyletic by Cheloderus G ray (O xypeltidae). Our study corroborates some relationships within C hrysomeloidea that were previously inferred from morphological data, while also reporting several novel relationships. The present work thus provides a robust framework for future, more deeply taxon‐sampled, phylogenetic and evolutionary studies of the families and subfamilies of C erambycidae s.l. and other C hrysomeloidea.     

The dynamics of male brooding,mating patterns,and sex roles in pipefishes and seahorses (family Syngnathidae)

Modern theory predicts that relative parental investment of the sexes in their young is a key factor responsible for sexual selection. Seahorses and pipefishes (family Syngnathidae) are extraordinary among fishes in their remarkable adaptations for paternal care and frequent occurrences of sex-role reversals (i.e., female-female competition for mates), offering exceptional opportunities to test predictions of sexual selection theory. During mating, the female transfers eggs into or onto specialized egg-brooding structures that are located on either the male's abdomen or its tail, where they are osmoregulated, aerated, and nourished by specially adapted structures. All syngnathid males exhibit this form of parental care but the brooding structures vary, ranging from the simple ventral gluing areas of some pipefishes to the completely enclosed pouches found in seahorses. We present a molecular phylogeny that indicates that the diversification of pouch types is positively correlated with the major evolutionary radiation of the group, suggesting that this extreme development and diversification of paternal care may have been an important evolutionary innovation of the Syngnathidae. Based on recent studies that show that the complexity of brooding structures reflects the degree of paternal investment in several syngnathid species, we predicted sex-role reversals to be more common among species with more complex brooding structures. In contrast to this prediction, however, both parsimony- and likelihood-based reconstructions of the evolution of sex-role reversal in pipefishes and seahorses suggest multiple shifts in sex roles in the group, independent from the degree of brood pouch development. At the same time, our data demonstrate that sex-role reversal is positively associated with polygamous mating patterns, whereas most nonreversed species mate monogamously, suggesting that selection for polygamy or monogamy in pipefishes and seahorses may strongly influence sex roles in the wild.     

Parental care behavior in the monogamous,sexually dimorphic Madagascar paradise flycatcher: sex differences and the effect of brood size

I studied the parental care behavior of the Madagascar paradise flycatcher Terpsiphone mutata in northwestern Madagascar. I especially focused on feeding, brooding and vigilance behaviors. Feeding rate did not differ between males and females, but females spent more time at the nest than males. Females dedicated their time to brooding, while males perched on the nest and were vigilant. Both parents changed the feeding rate in relation to brood size, so the feeding rate per nestling was not different among nests of different brood size. Duration of brooding by females increased with decreasing brood size, suggesting that the Royama effect, the pattern of lower feeding rate per nestling in larger broods, did not apply in this study. Males spent more time on vigilance than females. Anti-predator vigilance by males should be important for nestling survival given the high predation pressure typical of this population. In conclusion, males provide considerable parental care probably to minimize nestling starvation and to avoid nest predation. My results are not consistent with the general pattern of less parental effort by males in monogamous, sexually dimorphic species.