Research Article |
Corresponding author: Jiří Král ( spider@natur.cuni.cz ) Academic editor: Marielle Schneider
© 2022 Jiří Král, Ivalú M. Ávila Herrera, František Šťáhlavský, David Sadílek, Jaroslav Pavelka, Maria Chatzaki, Bernhard A. Huber.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Král J, Ávila Herrera IM, Šťáhlavský F, Sadílek D, Pavelka J, Chatzaki M, Huber BA (2022) Karyotype differentiation and male meiosis in European clades of the spider genus Pholcus (Araneae, Pholcidae). Comparative Cytogenetics 16(4): 185-209. https://doi.org/10.3897/CompCytogen.v16i4.85059
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Haplogyne araneomorphs are a diverse spider clade. Their karyotypes are usually predominated by biarmed (i.e., metacentric and submetacentric) chromosomes and have a specific sex chromosome system, X1X2Y. These features are probably ancestral for haplogynes. Nucleolus organizer regions (NORs) spread frequently from autosomes to sex chromosomes in these spiders. This study focuses on pholcids (Pholcidae), a highly diverse haplogyne family. Despite considerable recent progress in pholcid cytogenetics, knowledge on many clades remains insufficient including the most species-rich pholcid genus, Pholcus Walckenaer, 1805. To characterize the karyotype differentiation of Pholcus in Europe, we compared karyotypes, sex chromosomes, NORs, and male meiosis of seven species [P. alticeps Spassky, 1932; P. creticus Senglet, 1971; P. dentatus Wunderlich, 1995; P. fuerteventurensis Wunderlich, 1992; P. phalangioides (Fuesslin, 1775); P. opilionoides (Schrank, 1781); P. silvai Wunderlich, 1995] representing the dominant species groups in this region. The species studied show several features ancestral for Pholcus, namely the 2n♂ = 25, the X1X2Y system, and a karyotype predominated by biarmed chromosomes. Most taxa have a large acrocentric NOR-bearing pair, which evolved from a biarmed pair by a pericentric inversion. In some lineages, the acrocentric pair reverted to biarmed. Closely related species often differ in the morphology of some chromosome pairs, probably resulting from pericentric inversions and/or translocations. Such rearrangements have been implicated in the formation of reproductive barriers. While the X1 and Y chromosomes retain their ancestral metacentric morphology, the X2 chromosome shows a derived (acrocentric or subtelocentric) morphology. Pairing of this element is usually modified during male meiosis. NOR patterns are very diverse. The ancestral karyotype of Pholcus contained five or six terminal NORs including three X chromosome-linked loci. The number of NORs has been frequently reduced during evolution. In the Macaronesian clade, there is only a single NOR-bearing pair. Sex chromosome-linked NORs are lost in Madeiran species and in P. creticus. Our study revealed two cytotypes in the synanthropic species P. phalangioides (Madeiran and Czech), which differ by their NOR pattern and chromosome morphology. In the Czech cytotype, the large acrocentric pair was transformed into a biarmed pair by pericentric inversion.
haplogyne, inversion, NOR, rDNA, sex chromosome, speciation, Synspermiata
Spiders exhibit an enormous species diversity, paralleled by high karyotype diversity. However, despite considerable recent progress (e.g.,
Haplogyne araneomorphs (“haplogynes”) consist of the Synspermiata clade and two families, Filistatidae and Hypochilidae (
The present study focuses on the cytogenetics of pholcid spiders (Pholcidae), the most diversified haplogyne family with monocentric chromosomes. This family currently comprises almost 1900 described species in 97 genera (
We paid specific attention to the Macaronesian clade of Pholcus. Macaronesia consists of five volcanic archipelagos in the Atlantic Ocean, west of the Iberian Peninsula and northwestern Africa. Pholcus is among the most species-rich genera of Macaronesian spiders. The Macaronesian clade currently includes more than 20 described species that are largely restricted to the Canaries and Madeira (
Our aim is to determine the fundamental traits of karyotype evolution in European clades of Pholcus. Based on our new findings and on previously published data, we explore the congruence of individual karyotype markers with published phylogenies and discuss the possible evolutionary implications of karyotype transformations.
Information on the studied species (number of analyzed specimens, their sex, and locality data) is given in Table
Species studied, with specimen number, sex, and geographic origin. Abbreviation: sad = subadult.
Taxon | Individuals | Locality | GPS Coordinates (Latitude, Longitude) |
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P. crypticolens/opilionoides species group | |||
P. creticus | 4♂ | Greece, Crete, Topolia, Topolia cave | 35.4119, 23.6817 |
2♂ | Greece, Crete, Stavros, Lera cave | 35.5908, 24.1023 | |
P. opilionoides | 4♂ | Czech Republic, Veselí nad Lužnicí | 49.1506, 14.6930 |
P. phalangioides species group | |||
P. alticeps | 8♂ | Czech Republic, Chomutov | 50.4527, 13.4166 |
P. phalangioides | 1♂ | Portugal, Madeira, Santana | 32.8043, -16.8855 |
Macaronesian species group | |||
P. fuerteventurensis | 2♂ | Spain, Canariens, Fuerteventura, Giniginamar | 28.2024, -14.0734 |
P. dentatus | 1 sad ♂, 1♂ | Portugal, Madeira, Achadas da Cruz | 32.8390, -17.1907 |
P. silvai | 2♂ | Portugal, Madeira, Levada das 25 fontes | 32.7611, -17.1374 |
Chromosome preparations were obtained from testes of adult males by a modification of the spreading technique described by
The NOR pattern was determined by fluorescent in situ hybridisation (FISH) with a 18S rDNA probe from Dysdera erythrina (Walckenaer, 1802) (Dysderidae) (see
FISH was performed with the biotinylated 18S rDNA probe as described by
The male karyotype of all species studied had 25 predominantly metacentric chromosomes and the X1X2Y system (2n♂ = 25, X1X2Y). The X1 was the longest element of the set. Chromosomes X2 and Y were medium-sized elements of similar size. Chromosome pairs decreased gradually in length (Suppl. material
The chromosome pairs of the males of P. creticus comprised five metacentric (nos 1, 5–8), four submetacentric (nos 2,4,9,10), one subtelocentric (no. 11), and one acrocentric pair (no. 3). Sex chromosomes were metacentric except for the acrocentric X2 (Fig.
Pholcus crypticolens/opilionoides and phalangioides groups, male karyotypes (A–C stained by Giemsa D FISH). Based on sister metaphases II A P. creticus B P. alticeps C, D P. phalangioides (Madeira) C standard karyotype D karyotype, detection of NORs. Prepared from the same plate as the standard karyotype. Note four chromosome pairs with terminal NOR (nos 4,7,10,11) and the X1 chromosome with NOR at both ends. Pairs nos. 7, 10, and 11 are biarmed, pair no. 4 is acrocentric. NORs are localized at the long arm of these pairs. Scale bars: 10 μm.
Pholcus crypticolens/opilionoides and phalangioides groups, males, NOR detection A–E, G FISH F Giemsa staining A, B P. opilionoides A diplotene. Three bivalents contain NOR. There is also a signal on the sex chromosome trivalent. Y chromosome overcondensed. Note the scheme of sex chromosome pairing and scheme of the plate (particular elements separated by a dotted line) B two fused sister metaphases II. Note the terminal signal on five biarmed elements belonging to chromosome pairs. Odd number of chromosomes with signal suggests that NOR locus of one chromosome pair is heterozygous for NOR cluster. The X1 chromosome includes NOR at both ends C P. creticus, mitotic metaphase. Two chromosome pairs contain a terminal NOR. Y chromosome overcondensed. On the right side: scheme of the plate (particular chromosomes marked by a line). Inset: metaphase I, sex chromosome trivalent (without signal). Note the scheme of sex chromosome pairing D, E P. alticeps D metaphase I. Two bivalents contain NOR. There is also signal on the sex chromosome trivalent. Y chromosome overcondensed. Note the scheme of sex chromosome pairing E two fused sister metaphases II, Y chromosome overcondensed. NOR bearing elements: one pair of biarmed chromosomes (a terminal NOR), one pair of acrocentric chromosomes (a terminal NOR at long arm), X2 chromosome (a terminal NOR at long arm), X1 chromosome (NOR at both ends). Inset: X1 chromosome (from another plate), note the NOR at both ends F, G P. phalangioides, Madeira, metaphase I. Four bivalents include a NOR. There is also a signal on the sex chromosome trivalent. Note the scheme of sex chromosome trivalent. Abbreviations: a = chromosome of the acrocentric pair bearing NOR, b = bivalent containing NOR, bi = chromosome of a biarmed pair bearing NOR, c = centromere, ch = chromosome bearing NOR, s = sperm nucleus, SCT = sex chromosome trivalent, X1 = X1 chromosome, X2 = X2 chromosome, Y = Y chromosome. Scale bars: 10 μm except for insets (5 μm).
The chromosomes of the males of P. opilionoides exhibited the same morphology as in populations studied previously (
The male karyotype of P. alticeps consisted of metacentric chromosomes except for three submetacentric (nos 1,6,9), one subtelocentric (no. 5), and one acrocentric (no. 3) chromosome pairs as well as the acrocentric X2 chromosome (Fig.
The karyotype of the single male of P. phalangioides from Madeira consisted of metacentric chromosomes except for two submetacentric (nos 8 and 11) and one acrocentric pair (no. 4) as well as a subtelocentric X2 (Fig.
The karyotype of P. fuerteventurensis from the Canaries was composed of metacentric chromosomes except for one submetacentric (no. 1) and one acrocentric pair (no. 5) as well as an acrocentric X2 chromosome (Fig.
Pholcus, Macaronesian group, male karyotypes, stained by Giemsa. Based on sister metaphases II A P. fuerteventurensis B P. dentatus C P. silvai. Scale bars: 10 μm.
Pholcus, Macaronesian group, NOR detection A, C, D, F, G, I FISH B, E, H Giemsa staining A–C P. fuerteventurensis A metaphase I (a bivalent belonging to another plate is separated by a dotted line). One bivalent contains a NOR. There is also a signal on the sex chromosome trivalent. Note the scheme of sex chromosome pairing B, C two sister metaphases II separated by a dotted line. Note two terminal NORs, one on the long arm of the acrocentric pair and another one on the long arm of the acrocentric X2 chromosome D–F P. dentatus D metaphase I, one large bivalent contains a terminal NOR. Note the scheme of sex chromosome pairing E, F two fused metaphases II. Long arm of the acrocentric pair contains terminal NOR. Sister chromatids of chromosomes of this pair are sometimes associated by NOR clusters (see the right chromosome of the pair) G–I P. silvai G metaphase I, one bivalent involves a terminal NOR. Note the scheme of sex chromosome pairing H, I two metaphases II separated by dotted line. Long arm of the acrocentric pair contains terminal NOR. Abbreviations: a = chromosome of the acrocentric pair bearing NOR, b = bivalent containing NOR, s = sperm nucleus, SCT = sex chromosome trivalent, X1 = X1 chromosome, X2 = X2 chromosome, Y = Y chromosome. Scale bars: 10 μm.
In P. dentatus from Madeira, the chromosome pairs were metacentric except for two submetacentric (nos 7 and 11) and one acrocentric pair (no. 3). The sex chromosomes had a metacentric morphology except for the acrocentric X2 (Fig.
The chromosome complement of the second Madeiran species, P. silvai, had metacentric chromosomes except for one submetacentric (no. 8), one subtelocentric (no. 10), one acrocentric pair (no. 4), and an acrocentric X2 chromosome (Fig.
Both Madeiran species showed the same NOR pattern, namely a single locus at the end of the long arm of the acrocentric pair (Fig.
In general, the behavior of the sex chromosomes was characterized by positive heteropycnosis (i.e., more intensive staining) and association (i.e. close proximity of chromosomes without pairing) which transformed into pairing in some phases. The specific behavior of sex chromosomes was initiated as early as in spermatogonial mitosis. Sex chromosomes often exhibited positive heteropycnosis and a loose association in spermatogonial prophases, metaphases, and anaphases (Fig.
Pholcus, males, sex chromosome behavior at spermatogonial mitosis and first meiotic division, Giemsa staining A P. dentatus, spermatogonial metaphase. Note the association of positively heteropycnotic sex chromosomes in the middle of the plate B P. silvai, early spermatogonial anaphase, three half plates. Sex chromosomes exhibit a slight positive heteropycnosis and are placed in the middle of the half plates. Sex chromosomes are marked by arrows C P. fuerteventurensis, early diffuse stage. Sex chromosomes form a positively heteropycnotic body on the periphery of the nucleus D P. silvai, late diffuse stage. The sex chromosome body on the periphery of the nucleus exhibits positive heteropycnosis E P. fuerteventurensis, diakinesis (11 bivalents and a X1X2Y trivalent). The Y chromosome stained more intensively than the X chromosomes. Note the scheme of sex chromosome pairing F P. alticeps, diplotene (11 bivalents and a X1X2Y trivalent). Edge of another diplotene separated by dotted line. Note the scheme of sex chromosome pairing. Abbreviations: SCB = sex chromosome body, SCT = sex chromosome trivalent, X1 = X1 chromosome, X2 = X2 chromosome, Y = Y chromosome. Scale bars: 10 μm.
In the premeiotic interphase, the association of sex chromosomes transformed into sex chromosome pairing. The mode of sex chromosome pairing was most apparent during late prophase and metaphase I. Both ends of the metacentric sex chromosomes, X1 and Y, took part in pairing (Fig.
Pholcus, males, sex chromosome behavior in second meiotic division, Giemsa staining A P. silvai, two sister metaphases II. Metaphase II containing the X chromosomes is composed of 13 chromosomes. Metaphase II containing the Y chromosome comprises 12 chromosomes B P. alticeps, two sister anaphases II. Chromosomes X1 and Y display positive heteropycnosis. The X chromosomes are associated. The Y chromosome is placed in the middle of the half plates C P. fuerteventurensis, two sister metaphases II. Plate containing the X chromosomes is incomplete (1 chromosome missing). Note the positive heteropycnosis of the sex chromosomes. Abbreviations: X1 = X1 chromosome, X2 = X2 chromosome, Y = Y chromosome. Scale bars: 10 μm.
Pholcids are the most diversified family of haplogyne spiders with monocentric chromosomes and a suitable model group to study karyotype evolution. Their distribution is worldwide, and the available molecular phylogeny is the most comprehensive among all major spider families (
Here we focus on karyotype differentiation of the genus Pholcus. Previously published cytogenetic data concern seven species determined to species level and two species determined to genus level only (
Summary of Pholcus cytogenetic data. Doubtful data in bold. In most of these cases, it is possible to deduce probable correct information (in parentheses). †see
Taxon | 2n | SCS | Chromosome pairs: number, morphology | Sex chromosome morphology | NOR number (CP/SC) | NOR-bearing CPs: number, morphology (NOR location) | NOR-bearing sex chromosomes: morphology (NOR location) | References |
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bicornutus species group | ||||||||
P. pagbilao | 23 | X1X2Y | 7m+3sm | X1m+X2a+Ysm | 5/0 | 3 bi (t);1 bi (1 NOR p, t + 1 NOR q, t) |
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crypticolens/opilionoides species group | ||||||||
P. creticus | 25 | X1X2Y | 5m+4sm+1st+1a | X1m+X2a+Ym | 2/0 | 2 (t) | this study | |
P. crypticolens† | 24 | X1X20 | most or all m | X1?+X2? |
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(25) | (X1X2Y) | |||||||
P. manueli‡ | 25 | X0 (X1X2Y) | 11a | Xsm |
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P. opilionoides | 25 | X1X2Y | 6m+5sm | X1m+X2a+Ym | 3/2 | 3 bi (t) | X1 m (1 NOR p, t + 1 NOR q, t) |
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guineensis species group (+ P. bamboutos) | ||||||||
P. bamboutos | 23 | X1X2Y | most bi | X1m+X2m+Ym |
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P. kindia | 23 | X1X2Y | 8m+1sm+1st | X1m+X2m+Ym |
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Macaronesian species group | ||||||||
P. dentatus | 25 | X1X2Y | 8m+2sm+1a | X1m+X2a+Ym | 1/0 | 1a (q, t) | this study | |
P. fuerteventurensis | 25 | X1X2Y | 9m+1sm+1a | X1m+X2a+Ym | 1/1 | 1a (q, t) | X2 a (1 NOR q, t) | this study |
P. silvai | 25 | X1X2Y | 8m+1sm+1st+1a | X1m+X2a+Ym | 1/0 | 1a (q, t) | this study | |
phalangioides species group | ||||||||
P. alticeps | 25 | X1X2Y | 6m+3sm+1st+1a | X1m+X2a+Ym | 2/3 | 1 bi (t); 1a (q, t) | X1 m (1 NOR p, t + 1 NOR q, t); | this study |
X2 a (1 NOR q, t) | ||||||||
P. phalangioides (Czech cytotype) | 25 | X1X2Y | 9m+2sm | X1m+X2sm+Ym | 3/3 | 3 bi (t) | X1 m (1 NOR p, t + 1 NOR q, t); |
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X2 sm (q, t) | ||||||||
P. phalangioides (Madeiran cytotype) | 25 | X1X2Y | 8m+2sm+1a | X1m+X2st+Ym | 4/2 | 3 bi (q, t); 1 a (q, t) | X1 m (1 NOR p, t + 1 NOR q, t) | this study |
species determined to the genus level only | ||||||||
Pholcus sp. (India)§ | 26(?) | X1X20 (X1X2Y) |
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Pholcus sp. (Kazakhstan) | 25 | X1X2Y | 7m+3sm+1a | X1m+X2st+Ym |
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The ancestral pholcid karyotype probably consisted of 15 chromosome pairs and the sex chromosomes X1, X2, and Y (
The chromosome pairs of ancestral pholcids probably had a biarmed morphology (
The karyotype of the unidentified Pholcus sp. from Kazakhstan reported in
Closely related species of Pholcus often differ by the morphology of one or several chromosome pairs. For example, P. fuerteventurensis from the Canaries (belonging to the Macaronesian clade) differs from species of the same clade from Madeira by the morphology of three pairs. A possible apomorphy of P. fuerteventurensis is the transformation of the largest chromosome pair from metacentric to submetacentric. The Madeiran species show two possible synapomorphies, namely transformations of two metacentric pairs into submetacentric or subtelocentric. The first transformation concerned the 7th pair of P. dentatus and the 8th pair of P. silvai, respectively. The second transformation concerned the 11th pair of P. dentatus and the 10th pair of P. silvai, respectively (Suppl. material
A similar karyotype differentiation, where the morphology of one or more chromosome pairs changed while the number of chromosome pairs remained the same, has also been found in other pholcid genera (
All Pholcus species studied so far exhibit the X1X2Y system (
The genus Pholcus, like most other pholcids with the X1X2Y system (
The increase of Y chromosome size in pholcines has been accompanied by a reduction of the X2 chromosome. The X2 and Y chromosomes exhibit a similar size in the Pholcus clades analyzed in this study. The X2 chromosome is the most dynamic chromosome of the X1X2Y system in pholcids. It exhibits a considerable diversity in size and morphology (
Interestingly, Madeiran and central European specimens of P. phalangioides differed slightly in the morphology of the X2 chromosome. While the X2 chromosome of the Czech P. phalangioides was submetacentric (centromeric index 2.85), the X2 of the Madeiran specimen was subtelocentric (centromeric index 3.96) (
The sex chromosomes in Pholcus show a specific behavior in the male germline, which, like in other pholcids, includes positive heteropycnosis (more intensive staining), preferential location, and association or pairing. The association and heteropycnosis of sex chromosomes occur as early as during spermatogonial mitosis. Moreover, the sex chromosomes are usually located in the middle of spermatogonial plates, specifically on the metaphase plates (
Metacentric chromosomes of the X1X2Y system pair without chiasmata in male meiosis, namely by the ends of both arms (Silva et al. 2002;
So far, NORs have only been detected in a low number of spider species (see
The ancestral pattern of the subfamily Pholcinae probably involves three chromosome pairs with a terminal NOR each. Prior to the separation of Aetana Huber, 2005, a NOR locus appeared on one end of the X1. Thereafter, the NORs gradually spread to the other end of the X1 chromosome and to the end of the long arm of the X2, i.e., to the regions that ensure the achiasmatic pairing of the sex chromosomes. We assume that the sex chromosome-linked NORs (SCL-NORs) take part in this pairing (
Our study reveals a considerable diversity of NOR patterns in Pholcus. Based on data from Pholcus and the closely related genera, we suppose that the ancestral NOR pattern of Pholcus probably comprised two or three chromosome pairs with a terminal NOR locus each and three terminal X chromosome-linked loci (two on the X1 chromosome and one on the X2). The number of loci has then increased in some species and decreased in others (
A reduction in the number of NORs has occurred repeatedly in Pholcus, both on chromosome pairs and on chromosomes of the X1X2Y system. Thus, the Macaronesian clade exhibits a single acrocentric NOR-bearing pair. P. fuerteventurensis from the Canaries retained a single SCL-NOR located at the end of the X2 chromosome. The two Madeiran species share a degeneration/loss of SCL-NORs. In the P. crypticolens/opilionoides group, the reduction was more extensive in SCL-NORs than in NORs located on chromosome pairs. The pattern of P. opilionoides differs from the supposed ancestral pattern only by the absence of the X2-linked NOR, while the pattern of P. creticus is more derived, the SCL-NORs are degenerated/lost (this study). In P. pagbilao (P. bicornutus group), the number of NOR-bearing chromosome pairs has increased to four whereas SCL-NORs were degenerated/lost (
P. phalangioides showed intraspecific diversity of the NOR pattern and chromosome morphology. Considering NORs, the Czech cytotype exhibited the supposedly ancestral pattern of Pholcus (
The karyotype differences between the Czech and Madeiran cytotype were, however, more profound. They also differed in the morphology of some chromosomes. The chromosome pairs of the Madeiran cytotype showed the original pattern; they included a large acrocentric pair, which has changed to biarmed in the Czech cytotype. Furthermore, both cytotypes differed to some extent in the morphology of the X2 chromosome. Intraspecific differences in chromosome morphology have not been previously reported from pholcids. Whether the presence of different cytotypes is in any way related to the apparent COI polymorphism in this species (documented in the sequences deposited at NCBI) is unknown. The status of both cytotypes should be further analysed using larger samples and approaches of integrative taxonomy.
We present new data on karyotypes and meiotic division of seven species of the genus Pholcus (Pholcidae) from Europe. The selected species represent several different species groups within the region whose relationships among each other remain largely unknown. The male karyotype is composed of 25 chromosomes with a X1X2Y sex chromosome system. The sex chromosomes pair without chiasmata during male meiosis. The karyotypes are predominated by biarmed chromosomes. The karyotypes of most species contain an acrocentric chromosome pair, which has changed to biarmed in some taxa. This marker is either a synapomorphy of the species groups included in this study or a synapomorphy of the genus Pholcus. Closely related species usually differ in the morphology of one or several chromosome pairs, which suggests the operation of pericentric inversions and/or translocations. Such rearrangements have been implicated in speciation. The chromosomes X1 and Y show a metacentric morphology. By contrast, the X2 chromosome is usually acrocentric. NOR patterns are very diversified. In the ancestor of Pholcus, these structures were located both on chromosome pairs and on sex chromosomes. Sex chromosome-linked NORs could be involved in the pairing of sex chromosomes. Most of the analyzed species show a specific pattern of NORs. Nucleolus organizer regions have often been degenerated/lost during evolution. Remarkably, the loss seems to preferably affect SCL-NORs. The reason for this phenomenon is unclear. The rDNA sequences crucial for sex chromosome pairing might remain unaffected by the degeneration. P. phalangioides yielded two cytotypes, which differ in their chromosome morphology and NOR pattern. Some of the detected chromosome changes appear phylogenetically informative. Although the Macaronesian clade shows a very high rate of speciation, species of this lineage do not differ substantially in the number of chromosome changes from other analyzed lineages of Pholcus. However, this conclusion needs to be corroborated by an analysis of more species and species groups.
We are very thankful to our colleagues M. Forman (Charles University, Prague, Czech Republic) for improvement of the figures and valuable comments on the manuscript, T. Kořínková (Prague) and R. Angus (Natural History Museum, London, Great Britain) for inspiring discussion on the manuscript and correction of the English, S. Pekár (Masaryk University, Brno, Czech Republic) and D. Holá (Charles University, Prague, Czech Republic) for assistance with statistical evaluation of data, A. Roušar (Chomutov, Czech Republic) for collections of P. alticeps, and T.L. Heller (Ludwig-Maximilians-University, Munich, Germany) for participation in collection of P. creticus. Finally, we are obliged to the reviewers (L.M. Mola, University of Buenos Aires, Buenos Aires, Argentina; M.P. Rincão, Universidade Estadual de Londrina, Londrina, Brazil; and an anonymous reviewer) for their comments.
Our study was supported by the Czech Ministry of Education, Youth, and Sports (projects LTAUSA 19142 and SVV 260568: IMAH, JK) and the Chilean National Commission for Scientific and Technological Research (ANID) (IMAH). The collection of P. creticus by JK and JP was supported by a scholarship, which was based on agreement between the Czech Ministry of Education, Youth, and Sports and the Greek Ministry of Education, Lifelong Learning, and Religious Affairs. Fluorescence microscopy was performed in the Laboratory of Confocal and Fluorescence Microscopy, Faculty of Science, Charles University (Prague, Czech Republic). This laboratory is co-financed by the European Regional Development Fund and the state budget of the Czech Republic, projects no. CZ.1.05/4.1.00/16.0347 and CZ.2.16/3.1.00/21515, and supported by the Czech-BioImaging large RI project LM2015062.
Jiří Král https://orcid.org/0000-0002-6442-8554
Ivalú M. Ávila Herrera https://orcid.org/0000-0003-4387-5723
František Šťáhlavský https://orcid.org/0000-0002-8520-9166
David Sadílek https://orcid.org/0000-0001-6877-887X
Jaroslav Pavelka https://orcid.org/0000-0001-8834-7540
Maria Chatzaki https://orcid.org/0000-0001-7529-8962
Bernhard A. Huber https://orcid.org/0000-0002-7566-5424
Species studied, male karyotype data (including standard deviation)
Data type: Table (MS Excel file)
Explanation note: Abbreviations: parameters = parameters used to describe chromosome morphology [CI = centromeric index, RCL = relative chromosome length (% of TCL)], specimens = number of specimens used to obtain data (*specimens from Stavros were analysed). Chromosome morphology is indicated by background colour of a box (pink: metacentric, brown: submetacentric, dark blue: subtelocentric, light blue: acrocentric).