Corresponding author: Wayne P. Maddison (
Academic editor: J. Miller
The systematics of sitticine jumping spiders is reviewed, with a focus on the Palearctic and Nearctic regions, in order to revise their generic classification, clarify the species of one region (Canada), and study their chromosomes. A genome-wide molecular phylogeny of 23 sitticine species, using more than 700 loci from the arachnid Ultra-Conserved Element (
Maddison WP, Maddison DR, Derkarabetian S, Hedin M (2020) Sitticine jumping spiders: phylogeny, classification, and chromosomes (Araneae, Salticidae, Sitticini). ZooKeys 925: 1–54.
The jumping spider species long placed in the genus
Subtribe
This work’s three goals are to resolve sitticine phylogeny, to review the taxonomy of sitticines of one region (Canada), and to describe the remarkably diverse chromosomes of sitticines. Our immediate (and urgent) purpose in studying the group’s phylogeny is to settle its turbulent generic classification, which has seen, for instance, some well-known species change names three times in two years, for example, from
Until the last few years, most sitticines were placed in the single widespread and species-rich genus
Neither Prószyński’s “pragmatic” classification nor Breitling’s COI-based classification have promoted taxonomic stability in sitticines. Prószyński’s intentionally non-phylogenetic approach is particularly problematical. The great majority of systematists no longer use such “pragmatic” non-evolutionary classifications, as they are not anchored to a broadly predictive external reality: they are subject to the whims of biologists’ interests and the character systems they focus on. A taxon delimited for this sense of pragmatism carries with it no promise of meaning or utility, other than the promise it will bear the diagnostic characters chosen. Different choices of diagnostic characters would lead to different classifications, with no basis for selecting among different authors’ approaches except the weight of authority – in the end, not as pragmatic as a stable phylogenetic classification, which, by the implications of genetic descent, will predict trait distributions across the genome. Breitling’s approach might have dampened the instability, as it is phylogenetic and uses explicit data and analysis, but his choice of the single gene COI, without supporting morphological information, has yielded a classification in which we can have little confidence. Prószyński’s and Breitling’s reclassifications might have been steps forward had they been done in a group of salticids with almost no previous attention, but the sitticines are reasonably well studied and often mentioned in the literature. These sudden, comprehensive, conflicting, and largely baseless rearrangements of
Taxonomic instability yields confusion in ecological and other biodiversity literature about the identity of species studied, and damages the reputation of the taxonomic enterprise. We are now sufficiently capable of resolving phylogeny that we do not need to rely on the “pragmatic” choices of one authority or on a single misbehaving gene. Our goal is to provide stronger evidence, explicitly analyzed, for phylogenetic relationships in order to stabilize the classification of sitticines.
Preserved specimens were examined under both dissecting microscopes and a compound microscope with reflected light. Most of the coquille drawings were done in 1977 or 1978 using a reticle grid in a stereomicroscope. Colour drawings were done in 1974 through 1977 with a stereomicroscope and reticle grid. Pen and pencil drawings were made recently using a drawing tube on a Nikon ME600L compound microscope. Because some images were made decades ago, we are unable to supply scale bars on many. Terms used are standard for
Specimens were examined from the collections of the
Authors of nomenclatural acts in this paper vary by rank. For acts affecting the synonymy of genera (viz., reinstatement of
If not otherwise indicated, the authors of species names are given in the Classification section.
Taxa were sampled to cover a diversity of sitticine species groups from Eurasia, North America, and South America (Table
Specimens from which
Species | Specimen | sex | Locality | Reads Pass QC | Contigs | |
---|---|---|---|---|---|---|
|
d475 | f | Uruguay: Canelones: |
946351 | 207743 | 434 |
|
d490 | m | U.S.A.: California: |
1617332 | 360661 | 480 |
|
d482 | m | Canada: British Columbia: |
1471891 | 351670 | 588 |
|
RU18-7302 | f | Russia: Tuva: |
529905 | 151897 | 627 |
|
RU18-6432 | f | Russia: Tuva: |
406186 | 90846 | 626 |
|
d487 | m | Canada: Ontario: |
1370738 | 299273 | 564 |
|
d480 | m | Canada: British Columbia: |
1489551 | 303924 | 579 |
|
d488 | m | Canada: Saskatchewan: |
1466702 | 303612 | 606 |
|
RU18-6799 | m | Russia: Tuva: |
261947 | 60612 | 653 |
|
ARV4504 | m | Italy: Stilfs | 16385503 | 42677 | 515 |
|
RU18-7308 | f | Russia: Tuva: |
468358 | 110900 | 649 |
|
d483 | m | Canada: British Columbia: |
1316697 | 279173 | 503 |
|
d491 | m | Poland: Cisna near Lesko | 187507 | 58418 | 312 |
|
d492 | m | Poland: Bukowksa Kopa | 418777 | 137114 | 397 |
|
d512 | m | Germany: Saxony: |
416618 | 113416 | 591 |
|
d489 | m | U.S.A.: California: |
1289981 | 278727 | 506 |
|
RU18-5346 | m | Russia: Novosibirsk Oblast: |
306744 | 72547 | 668 |
|
d493 | m | Poland: Grabarka |
338718 | 113167 | 408 |
|
RU18-5156 | m | Russia: Novosibirsk Oblast: |
435654 | 93640 | 627 |
|
d471 | f | Uruguay: Lavalleja: |
646088 | 248616 | 549 |
|
d472 | m | U.S.A.: Arizona: |
1015130 | 250378 | 448 |
|
d479 | f | Argentina: Neuquén: |
981935 | 268639 | 497 |
|
d473 | m | Ecuador: Orellana: |
1419103 | 289905 | 469 |
|
d474 | m | Ecuador: Orellana: |
3513351 | 723782 | 607 |
|
d478 | f | Uruguay: Maldonado: |
121131 | 61298 | 109 |
|
d481 | m | U.S.A.: Oregon: |
1529835 | 322636 | 536 |
|
d476 | m | Ecuador: Manabí: |
2524270 | 710859 | 651 |
|
d477 | m | Ecuador: Napo: |
1211674 | 256367 | 582 |
For most samples, DNA was extracted from multiple legs using the Qiagen DNeasy Blood and Tissue Kit (Qiagen, Valencia, CA) following manufacturer’s protocol. Specimens d491 and d492 of
In the resulting set of loci, most taxa have over 100,000 base pairs of sequence data, but some are less thoroughly sequenced. The less thoroughly sequenced taxa are:
This pipeline therefore resulted in two collections of genes, one of 968 loci for all the taxa (“All Taxa”), the other of 957 loci for the core set of well-sequenced taxa (“Core Taxa”). A filter of occupancy was then applied, eliminating all loci which had sequences for fewer than seven of the 20 well-sequenced taxa of the ingroup (
Maximum likelihood phylogenetic analyses were run using IQ-TREE version 1.6.7.1 (
A separate small phylogenetic analysis was done to explore the distinction in
Sequence reads are deposited in the Sequence Read Archive (BioProject submission ID PRJNA605426,
Chromosomes were studied in 17 taxa of
Meiotic chromosomes were observed in testes of adult and subadult males using Feulgen staining, following the methods of
Evidence for scoring chromosome complement of each species is described in Chromosome observations. Most chromosome scoring was done from meiotic nuclei in first metaphase or diakinesis showing chromosomes that are well separated, or, if overlapping, easily interpretable. Although well-spread mitotic nuclei would have added useful data, we judge meiotic chromosomes to be sufficient as they show distinctive features, e.g. when they are oriented by the centromere pulling toward the pole on the metaphase plate. Metacentrics show an obvious bend at the centromere where the second arm hangs loose like a dog’s ear (Fig.
In describing chromosome complements, we use “a” and “m” to indicate one-armed (acrocentric/telocentric) and two-armed (metacentric/submetacentric) chromosomes respectively. Thus, “26a+XaXa0” would mean “26 acrocentric autosomes plus two X’s, both of which are acrocentric”. In all cases, the multiple Xs of a male are interpreted as not being homologous, and therefore it would be more proper to refer to the systems as X1X20, X1X2Y, or X1X2X3Y rather than as XX0, XXY, or XXXY. However, the “1”, “2”, “3” will be left implicit, omitted for ease of reading, to avoid overly complex labels like Xa1Xa2Xa3Ym.
The maximum likelihood tree from the
The phylogeny of
Our
Although
The deep branches of the Eurasian Radiation are short, suggesting the group diversified rapidly. Nonetheless, the monophyly of subgenus
The relationships among
The phylogenetic results lead us to revise the generic division of sitticines. Unless we are to put all
Here we give a taxonomic review of the tribe, focussing especially on the species in Canada, and the two new species used in the molecular phylogeny (
Amycoid salticids with fourth legs much longer than third and retromarginal cheliceral tooth lacking. Ancestrally they were ground-dwellers in the Neotropics, later diversifying in Eurasia to include species that live on tree trunks (e.g.,
Eleven genera are here recognized in the
Despite the synonymy of
This group of five Neotropical genera was first recognized by
There are no known morphological synapomorphies of this subtribe, but the molecular data show clearly that the five genera listed here form a clade. There are two major subgroups according to the
We unite the primary Eurasian radiation under the single genus
Our choice to consider all but two Eurasian species as belonging to
The appropriate name for this unified genus is
However, there is value in offering a weaker recognition of three subgroups of
The three subgenera have subtle but mostly consistent morphological differences.
Subgenus
Subgenus
Subgenus
Figures
Body generally more compact than in subgenus
Five species of
(all in
A widespread Holarctic species often found in retreats in dry flower heads in wetter areas such as marshes,
We treat the North American populations as full
The results of our COI analysis of Palearctic and Nearctic
Within North America, the characterization of
A more serious confusion apparently occurred with the labelling of type specimens of
At stake is not the name used for the common white-striped species (which would be
Canada: British Columbia: Richmond (2 females),
A widespread but little-known Nearctic species,
Both males and females have shorter legs and less contrasting markings than in
(all in
We reinstate
(all
A Sibero-American boreal species that is little collected, resembling closely
Canada: Northwest Territories: Wrigley (1 female,
Figures
The species placed here, despite having palpi with very different embolus lengths, share a similarly narrow and high body with relatively long legs (Figs
Maximum likelihood phylogeny from 757 concatenated
Sitticines of Canada:
The natty contrasting black-and-white markings distinguish
(all
This species, introduced to North America apparently in the middle of the 20th century (
(all in
Although closely related to
(All in
Sitticines of Canada:
The single species
We have chosen not to subdivide the Neotropical
The
Small species from southern North America, related to the
A small unmarked leaf litter species, known best from the southeastern United States, but recently reported from Canada in the BOLD barcode database (Ratnasingam and Hebert 2007, 2013), from the extreme southern point in Ontario (Point Pelee National Park, specimens PPELE142-11, PPELE183-11, CNPPE2332-12, PPELE666-11, PPELE644-11).
Prószyński (2017a) rejected
U.S.A.: Florida: Gainesville (1 male, 1 female,
Sitticines of Canada: the
Relationships among
While females of this small Southwestern desert-dwelling species are indistinctly unmarked, males tend to be reddish with a narrow central longitudinal stripe (Figs
Canada: British Columbia: Summerland (1 male,
Epigynes of
Figures
A Neotropical group, consisting of two species groups, the small glabrous or shiny
Male holotype and 2 male, 3 female paratypes from Ecuador: Orellana: Río Bigal Reserve, main camp area.
Refers to the copper colour of males.
A species common in eastern Ecuador on disturbed open grassy ground. It was used in the molecular phylogenetic study of
Differs from the very similar
22 males and 6 females from: Ecuador: Napo: Tarapoa. 23 June – 1 July 1988 W. Maddison WPM#88-002 (1 male); Ecuador: Napo: bridge over Rio Cuyabeno on road to Tipishca. 25–30 June 1988 W. Maddison WPM#88-004 (1 male 1 female); Ecuador: Napo: bridge over Rio Cuyabeno on road to Tipishca. 29–30 July 1988 W. Maddison WPM#88-018 (4 males 2 females); Ecuador: Napo: Reserva Faunistica de Cuyabeno, Laguna Grande, Sendero La Hormiga. 2–5 August 1988 W. Maddison WPM#88-023 (2 males); Ecuador: Napo: Reserva Faunistica de Cuyabeno, Laguna Grande, PUCE field station. 1–7 August 1988 W. Maddison WPM#88-025 (1 male); Ecuador: Napo: bridge over Rio Cuyabeno on road from Lago Agrio to Tipishca. 8–9 August 1988 W. Maddison WPM#88-027 (1 male); Ecuador: Sucumbios: Reserva Faunistica Cuyabeno, Laguna Grande, PUCE field station.
The Holarctic
Canada: Northwest Territories: Tuktoyaktuk (1 male); Nunavut: Baffin Island (1 female); British Columbia: Downton Creek (2 males 2 females),
Figures
A Neotropical group whose male spermophore (with some possible exceptions) has a “shortcut loop”. That is, the large loop of the spermophore that normally occupies much of the visible face of the tegulum, and which points basally in many sitticines (e.g., Fig.
The phylogeny strongly places
The placement of
We synonymize
Male holotype, 10 male and 8 female paratypes from Ecuador: Manabí: Puerto Rico, Cabañas Alandaluz 5 May 1994 W. Maddison WPM#94-031. The holotype (specimen
Based on the type locality; the form is the adjective in Spanish (masculine or feminine).
A species on the beaches of coastal Ecuador, resembling
Palp closely resembles that of
15 males and 7 females from Ecuador: Manabí: Machalilla National Park, Salaite, between HWY and coast 6 May 1994 W. Maddison WPM#94-032 (4 males, 2 females); Ecuador: Manabí: Machalilla National Park, Salaite, 1 km inland along trail from HWY. 6 May 1994 W. Maddison WPM#94-033 (3 males); Ecuador: Manabí: Machalilla National Park, trail between Agua Blanca & San Sebastien 50–400 m dry forest 7 May 1994 W. Maddison WPM#94-034 (1 male); Ecuador: Manabí: Crucita. 30 August 1988 W. Maddison WPM#88-040 (2 males 4 females); Ecuador: Del Oro: Jambelí 13 August 1989 W. Maddison WPM#89-040 (3 males); Ecuador: Manabí: Puerto Lopez.
The following species are not sitticines, indicated by the presence of retromarginal cheliceral teeth (lacking in the
The following three are members of the
The following two species described in
The following species can be moved out of
Table
Chromosome complements observed for males of 17–18 species of sitticines. The autosomal counts represent diploid complement, and thus 26a means 13 pairs of acrocentric autosomes. In the chromosome counts, a = acrocentric (one-armed), m = metacentric (two-armed). Exx. is the number of specimens; nuc. is the number of nuclei showing the full chromosome complement; +nuc sex is the number of additional nuclei showing the sex chromosomes (though not clearly the autosomes). Uncertainties about scoring, in particular about
|
|
♂ |
|
|
|
|
+ |
|
|||||||
|
14m | Xm0 | no | U.S.A.: Gainesville, |
1 | 6 | 2 |
|
26a? | XaXa0? | ? | U.S.A.: Dillon Cr., |
3 | 11 | |
|
26a | XaXa0 | no | Ecuador: Tarapoa, |
1 | 2 | 1 |
|
24a | XmXaYm | yes | Canada: Leguil Creek, |
2 | 10 | 1 |
Canada: Inuvik, |
1 | 1 | |||||
Canada: Wawa, |
2 | 8 | |||||
U.S.A.: Mt. Monadnock, |
1 | 3 | |||||
|
24a | XaXaXaYm or XmYaYaYa | yes | Switzerland: Flims, |
3 | 14 | 10 |
|
26a | XaXa0 | no | Ecuador: Crucita, |
1 | 3 | 2 |
|
|||||||
|
26a | XaXa0 | no | Canada: Toronto, |
3 | 9 | 1 |
Russia: Uvs Nuur, |
2 | 11 | 6 | ||||
|
? (28a?) | XaXa0 | no | Russia: Uvs Nuur, |
1 | 1 | 7 |
|
26a | XaXa0 | no | 38.6, 34.8 ( |
– | ||
|
26a | XaXaYa | yes | Canada: Inuvik, |
1 | 3 | 4 |
|
28a | XaXa0 | no | Canada: Barrie, |
1 | 7 | 7 |
U.S.A.: Naselle, |
1 | 2 | |||||
|
24a? | XaXaXaYm? | yes | Switzerland: Flims, |
1 | 3 | 5 |
|
26a | XaXa0 | no | Russia: Uvs Nuur, |
2 | 13 | 5 |
|
24a | XaXaXaYm | yes | U.S.A.: Ponemah, |
1 | 5 | 6 |
|
26a | XaXa0 | Canada: Burlington, |
3 | 16 | ||
|
28a | XaXa0 | no | Canada: Nipigon, |
1 | 4 | |
Canada: Sault Ste. Marie, |
1 | 1 | |||||
Canada: Chinook L., |
1 | 8 | 3 | ||||
|
26a | XaXmYa | yes | U.S.A.: Cambridge, |
4 | 10 | 9 |
|
26a | XaXa0 | no | Russia: Karasuk, |
1 | 9 | 14 |
26a | XaXa0 |
|
– |
Chromosomes of first meiotic division in males of the
All four sex chromosomes of
Chromosomes of first meiotic division of
Chromosomes of meiosis of
Chromosomes of meiosis of
While salticids are fairly conservative in basic chromosome complement, with most species showing 26 acrocentric autosomes and X1X20 sex chromosomes (
Chromosome evolution in sitticines. Ancestral nodes show the most parsimonious reconstruction of the evolution of Y via X-autosome fusions (black) from the X1X20 sex chromosome system (white). Phylogeny from Figure
The ancestral autosome number in sitticines is unclear. Among the species with XX0, some have 26 autosomes, others have 28. Assessing a comparable autosome number with neo-Y species requires interpretation, as the neo-Y system itself binds one or more autosomal pairs with the X chromosomes, as indicated in part by distinctive condensation patterns. If (as in
An unanticipated but consistent correlation between base autosome number and the presence of neo-Y is seen in Fig.
If these small chromosomes are supernumerary (B) chromosomes, it is possible that there is considerably more variation within species than our small sample sizes can detect. Undetected intraspecific variation in autosomes or sex chromosomes would not negate our basic evolutionary conclusions. Were we to find species variable with respect to the presence of a neo-Y chromosome, for example, it would point to even more transitions between XX0 and XXY/XXXY.
Our uncertainty about chromosome complement in some species does not strongly affect our conclusions about homoplasy or correlations, though it could affect a detailed reconstruction of the evolution of autosome number, or of particular fusions involved in a neo-Y system. For instance, if we delete autosome number for
Chromosome evolution of sitticines will not be well understood, however, until a larger sample of species and specimens is obtained, given the high diversity seen in our small sample. Our data hint to the possibility of rapid evolution provoked by special mechanisms.
We are grateful to several colleagues who made special efforts to provide us access to specimens: to Galina Azarkina for greatly facilitating collecting in Siberia, to Gergin Blagoev for preparing and taking photographs of